The single best feature in Apple’s second-generation iPhone 3G isn’t the increased speed or the GPS location-finding feature. It is something called the “App Store,” a clever distribution mechanism for third-party programs that can run on the iPhone and on its close cousin, the iPod Touch. And you don’t even need a new iPhone to get the App Store. It is also part of a free software upgrade for older iPhones and a $10 upgrade for the Touch.

Scrabble is just one of the many ‘apps’ available for the iPhone and iPod Touch.

In just the first 10 days since the new iPhone and the App Store launched on July 11, more than 900 programs — applications, or “apps,” in tech jargon — have been introduced by numerous developers. Over 90% cost less than $10 or are free.

Even more noteworthy: iPhone and Touch users have downloaded 25 million copies of these programs, ranging from silly sound effects to challenging games; from news readers to restaurant locators; from social-networking programs to business applications.

We have been furiously downloading and trying out scores of these programs, using a new iPhone 3G, an original iPhone and an iPod Touch, and in general, we are very impressed. We found the process of choosing and downloading apps to be easy and quick, and most of the programs to be useful or entertaining. The vast majority are nicely designed, with great graphics and effective, simple user interfaces.

The easy availability of so many programs written by developers beyond Apple (AAPL) itself makes the iPhone a true computing platform, like a pocket-sized Windows or Macintosh PC. With so many programs already available, and many more in the pipeline, iPhone and Touch owners can have a device with fresh, different capabilities every day.

But the process isn’t perfect. For one thing, it is controlled by Apple, which can theoretically bar a program from distribution or take its time making one available.

There are also some glitches. If you download a lot of apps in a short period, it can slow the phone’s next synchronization with iTunes to a crawl, while iTunes tries to back up all the new programs, each of which can contain numerous hidden files. And there’s a bug in the new iPhone operating system that causes apps to crash, and can even force the iPhone or Touch to reboot, if you use a large number of the new apps in quick succession. Apple says it is working on fixing the latter problem.

Also, Apple’s claim of over 900 programs is somewhat misleading, because more than 100 of those are individual books you can read on the phone.

Apple’s baby isn’t the first smart phone that has attracted developers. Thousands of third-party programs already exist for Nokia (NOK) phones, BlackBerrys, and phones running the Palm (PALM) and Windows Mobile operating systems. But, compared with the graphically rich, snappy iPhone apps — many of which fetch data from the Internet at high speed — the typical program on these older platforms looks positively primitive.

AOL’s AIM program

The App Store can be accessed either from the device itself or from Apple’s iTunes software on a Windows or Mac computer, which then transfers the app to the iPhone or Touch. The programs cover a wide range.

Some fill in obvious holes in Apple’s original complement of iPhone software, things the iPhone has lacked that other phones have. These include AOL (TWX) Instant Messenger, a variety of task and to-do lists, sophisticated note takers and a voice dialer. There are numerous versions of popular board, card and word games, like solitaire, mahjong, Scrabble and Sudoku. There are also eye-popping iPhone versions of popular video games, some controlled by the phone’s motion detectors, which allow you to move cars and characters by just tilting the phone.

Numerous programs let you perform Internet functions without using the Web browser on the iPhone or iPod Touch. These include news readers, Internet radio players, sports-information apps, and programs that let you blog or use Google (GOOG) or Facebook or MySpace.

There are business programs from Oracle (ORCL), Salesforce.com and Bloomberg. And there’s a clutch of Bible programs.

Some are simply goofy, like a virtual Star Wars-like lightsaber, a rotary-phone dialer and a virtual “stapler.” And several programs turn the phone into a flashlight for emergencies.

There are way too many interesting apps to review here, but these are some we liked, in no particular order.

AOL Radio

AIM: free

This version of AOL’s popular instant-messaging program does a competent job with text chat, though it can’t yet do video or audio chats, or transfer files. Because Apple isn’t allowing third-party programs to run constantly in the background, you can’t receive new messages in AIM while doing other things. This will supposedly be fixed by new Apple technology due later this year.

AOL Radio: free

While the iPhone and Touch contain full, terrific iPod capabilities, they don’t come with Internet radio players like this one. It can stream music and talk from a wide variety of online sources, including the Internet versions of broadcast radio stations.

Evernote: free

This is an elegant note-taker that has been on computers for a while. You can jot down text notes, store photos or dictate audio memos. And it synchronizes with your Evernote account on Windows or Mac PCs or the Web.

Instapaper: free

A handy way to store Web pages on your iPhone or Touch for reading when you’re offline. While on your computer, an Instapaper button added to the Web browser can snag Web pages for your personal Instapaper database. Then, when your iPhone or iPod Touch is online, it synchronizes with the Web-based Instapaper database. Later, when you’re offline, the pages are still there on the device, ready to read.

Travelocity TravelTools: free

You can use this to check flight schedules, gate assignments and security waiting times. While you can’t book flights through this app, there’s a button that automatically calls Travelocity’s toll-free booking line.

More Cowbell!: free

This is inspired by the Christopher Walken/Will Ferrell Saturday Night Live skit, which made the lowly cowbell a cult musical instrument. Whenever you tap the on-screen cowbell, it makes the recognizable, hollow sound heard in songs like “Down on the Corner,” by Creedence Clearwater Revival. You can play along with any song you choose on the iPod Touch or iPhone.

Touch Tarot: $0.99

Touch Tarot

Touch Tarot is a digital tarot-card reading that takes place on your iPod Touch or iPhone, instead of at a table inside an incense-scented tent at the county fair. Phrasing above each card tells its general category, and below each card is a brief explanation of its meaning. For example, we turned over the Wheel of Fortune card in one card reading, and it said, “Advancement for good or ill. The unexpected may occur. Good fortune.”

iWant: free

The iWant app displays 12 black-and-white icons on your device’s screen, each representing a different category of something you might be looking for — including restaurants, bars, cafés, hotels, drugstores, banks, car rentals and movies, among others. The device identifies your location, and each category can be tweaked to search by distance or highest rankings from Yelp, a user-written rating service.

Urbanspoon: free

Urbanspoon resembles a slot machine: From left to right, columns show the location, cuisine and cost of nearby restaurants. Instead of pulling a lever to start the slot machine, you simply shake your iPhone or iPod Touch whenever you want to find a restaurant. When it stops, you see the name of a restaurant near you and its classification in each category. (You can also specify what location, cuisine or cost you’re looking for.)

Air Hockey: $0.99

Air hockey works like the game you used to play in your best friend’s basement. You play against the computer, using a fingertip to push red or blue mallets that move a puck around the screen-turned-table and trying to sneak the puck past your computer opponent to score a goal.

MotionX Poker: $4.99

MotionX Poker

This is an addictive poker game, played with realistic, beautifully rendered dice instead of cards. The cool thing is that you roll the dice by simply shaking the iPhone or iPod Touch; convincing sound effects accompany each roll of the dice.

MLB.com At Bat: $4.99

There are lots of cellphone apps and services that can give you live updates on baseball games. What’s special about this one is that it adds video clips of key plays that you can view while the games are still in progress, using the full power of the gorgeous screen and video player on the iPhone and the Touch.

Crash Bandicoot Nitro Kart 3D: $9.99

This is a rollicking, fun iPhone and iPod Touch rendition of the classic video racing game, where you control your car by tilting the phone. The graphics are good, and the game-play is responsive.

Truphone: free

This is the first app for the iPhone that allows you to make cheap phone calls over the Internet instead of using the built-in cellphone capability, which can be much costlier, especially for international calls. In our tests, we had some trouble at first, but after we removed and re-installed the program, it worked fine. Calls to 40 countries are six cents a minute to landlines and 30 cents a minute to cellphones. The iPod Touch lacks a microphone, so this app works only on the iPhone.

Write to Walt and Katie at mossbergsolution@wsj.com

To make Bluetooth even easier to use in cars, most new luxury cars and some standard cars are sold with optional built-in Bluetooth speakerphone technology which doesn’t even require an earpiece. Some cars also come with built-in iPod integration, displaying song titles on the dashboard and controlling the iPod using buttons on the steering wheel, again to minimize distractions. One new built-in product, SYNC, the voice-activated system created by Ford Motor Co. and Microsoft Corp., lets users do both things hands-free: play music or make phone calls using simple voice commands.

The $120 Parrot PMK5800 uses voice recognition for a more hands-free experience.

This week, I tested two devices that bring Bluetooth technology to older cars in hopes of integrating hands-free phone calls and music with a car’s stereo system. I tried the $130 Venturi Mini from NextGen Venturi Ltd. (www.myventuri.com) and $120 Parrot PMK5800 from Parrot Inc. (www.parrot.com) on three cars made in 2000 and 2005.

Neither device offers a surefire solution; each is limited by your particular car and cellphone. But the Parrot sails ahead of the Venturi Mini by using voice activation for phone calls, something the Venturi Mini can’t do. Venturi’s version of “hands-free calling” requires initiating a call on the cellphone itself or by looking down at a tiny, grayscale screen and painstakingly scrolling through names of contacts. Furthermore, the Parrot worked after only a few steps, while the Venturi took much longer to set up and get going.

Both of these are one-piece black gadgets that plug into your car’s cigarette lighter and use FM transmitters to play on unused FM radio stations. Each has a tiny screen, though the Parrot screen is used solely to display the current station so as to match it with the radio. The idea is that after initially “pairing” a Bluetooth cellphone with one of these devices, the phone and device will automatically find each other whenever both are in the car and on, making calls easier and music a bit more hands-free.

The Parrot and Venturi Mini will only play music via Bluetooth using cellphones that have a technology called A2DP, which enables music streaming. More and more new cellphones have this technology, such as the Nokia 6555 that I used, but many — including Apple’s iPhone — don’t. Most people will play music by attaching an iPod or other portable music player to these devices using cables that come with them.

The $130 Venturi Mini doesn’t work with voice commands.

Neither the Venturi Mini nor the Parrot PMK5800 enable voice commands with music: songs streamed via Bluetooth are controlled using buttons on the devices, and music coming from a wired-attached player can only be operated using buttons on that player.

The Parrot isn’t as compact or as stylish as the Venturi Mini, but its best feature is unseen: built-in voice recognition software that guides you while using this device. If your cellphone has built-in voice-recognition software, which many do, you can plug in the Parrot and get started. Otherwise, contacts must be loaded on to the Parrot and assigned a voice tag. Large green and red buttons initiate or end phone calls, but speaking commands also works. A knob turns to different stations or can be pressed and turned for audible descriptions of menus. Three glowing Play/Pause, Skip Ahead and Skip Back buttons are easy to find without looking down so as to navigate through music.

While I was listening to music coming from one paired cellphone, my sister called me on another paired cellphone that I had forgotten I had in my purse. The music automatically paused, and the sound of a ringing phone came from the car speakers until I answered it by pressing the Parrot’s green button (speaking the word “phone” also works).

If voice tags are assigned to contacts in your phone, the name of the person calling can be announced over the speakers, like caller ID. Music automatically re-starts after a call ends.

I made calls on the Parrot by pressing its green button and speaking directions like “Call Allison Mobile” to call the correct number from my phone’s contact list. The voice recognition sounded a bit robotic, but almost always found the right number.

Most voice calls sounded rather clear to the people with whom I spoke, but in the car, calls suffered when stations were interrupted with static as I drove around the Washington, D.C., area. One major issue with relying on FM transmitters in major cities is the small number of unused radio stations. Static also affected streamed music, making it sound scratchy at times. Music playing from a cord-connected iPod had no trouble.

The same static problems arose with Bluetooth calls and music on the Venturi Mini. This device’s rectangular face has a scroll button in its center, which seems like it would be a useful addition. But this can’t be pressed down to select anything on the screen, which is maddening. Instead, selecting anything from the Venturi screen must be done using a separate button, as if it wasn’t even designed to be a hands-free device.

To set up the Mini, a paired phone’s contacts must be copied from the phone onto the device. Once these contacts are added, calls can be initiated through the device by finding the correct name on the screen using the scroll wheel and pressing more buttons to select that name and place the call. None of this involves voice recognition, and it’s all supposed to be done while you’re driving.

For all its faults, the Venturi does have a few features that the Parrot doesn’t, including the ability to display Bluetooth data — like the name or number of an incoming caller and a song title and artist — on your radio display if your car has this ability. But most older cars don’t allow this, and I couldn’t quickly figure out how it worked even while driving in a 2005 car. You can also charge devices through the Mini using a built-in USB port.

The position of a car’s cigarette lighter matters to the Venturi Mini and the Parrot. This plug is often positioned near the gear shift, and in my manual car, it would’ve been difficult to operate these gadgets while in fifth gear (I didn’t try). The location of this plug also determines how loud or soft your voice sound to callers. So as to not sound so far away during calls I tried to lean closer to the devices, but this isn’t safe while driving.

The Venturi Mini looks like a hip device, but without voice recognition software and a smart interface, it’s frustrating and dangerous to use. Parrot’s PMK5800 plugs in and works and its voice-recognition software makes it a true hands-free device that will improve the way you use Bluetooth in your car. Just look out for static, especially in big cities.

Edited by Walter S. Mossberg

Email mossbergsolution@wsj.com