But even though you can use these services without leaving home, many of them still require you to go to a specific Web site — one you wouldn’t necessarily visit regularly. Sites like Gazelle.com and Venjuvo.com that pay cash for old electronics (or just recycle them) aren’t exactly online destinations.

Now one of those ways to unload your stuff involves a Web site you might visit many times a day. A site that has considerable sway in the social-networking world, where over 175 million active users go to share personal stories, photos and videos with hundreds of “friends.”

That’s right, I’m talking about Facebook. Tuesday, the social-networking giant announced its new Facebook Marketplace, Facebook.com/Marketplace, an integrated application powered by Oodle, known for its work with online classified ads. Marketplace uses colorful icons to represent four actions you can take in its app: Sell It; Sell for a Cause; Give it Away; and Ask for It.

Facebook Marketplace users can pick from 12 categories of listings, as well as buy or sell items for a favorite cause.

Oodle granted me early access to the Marketplace app before it became available Tuesday. A friend of mine and I were both set up with test accounts so that we could see one another’s fake Marketplace items and interact with one another within Marketplace; hundreds of Oodle employees also were testing this. (It was fun to see what people offer for sale when they’re just pretending, like one person who offered to sell everything on a colleague’s desk when he was out.)

Facebook’s original iteration of Marketplace started back in 2007, but was geared toward services like housing and jobs. The Oodle-powered Marketplace is merchandise-centric and includes more detailed organization, deeper integration with Facebook, and ways to buy or sell things to raise money for 1.7 million causes.

It still lacks a built-in electronic payment system, such as PayPal or Discover card, for exchanges between users or donations to causes. Instead, Marketplace encourages its users to exchange money however they choose, like traditional classified ads. And that could cause some obvious problems. For instance, if an item were sold for a cause, the seller could later donate the amount via credit card after closing a listing. But there’s no guarantee that the seller will actually do this. Oodle says it will listen to feedback from the Facebook audience and will try to integrate e-payments, if preferred.

Every posted item can include a location, description, category, photo and an explanation of why it’s in the Marketplace. Each item is reviewed by Oodle’s fraud-detection program, which looks for inappropriate content and suspicious activity, and a post could take up to 30 minutes to appear online after you submit it. My posts displayed almost instantly in the Marketplace newsfeed. Users also can opt to publish their posts to their Facebook profiles.

One example of Marketplace’s newly detailed organization comes in its browsing options. The old version of Marketplace had options to browse through jobs and housing, but not specific categories of items for sale. Now, users can browse through 12 categories of specific items including “Home & Garden,” “Baby & Kid Stuff,” “Tickets” and “Musical Instruments.” Items that don’t fit into these 12 categories are put into an “Everything Else” category.

Each item in Marketplace integrates with Facebook’s familiar format, like having its own online “wall” where questions and comments appear. If you’re looking for something in Marketplace by using the “Ask for It” option, you can recruit people to help you find the item by selecting from your list of friends, which works the same way people can suggest Facebook people to friends who might know them. Glancing at an item shows the seller’s profile photo, a link to all of the person’s listings and a brief history of his or her overall Marketplace activity, such as “3 listings in the last month.”

The integration of charitable causes into Marketplace gives supporters new ways to raise money for a favorite group like the World Wildlife Fund or Habitat for Humanity International. On the Marketplace home page, causes are displayed in a right-hand panel with a daily featured cause. This Featured Cause shows who else supports it and how many items you can buy or sell to support it.

Privacy is a natural concern in online marketplaces. By default, your posted listings are visible to any Facebook member in Marketplace. Users can opt to remain anonymous — they’re listed as “Facebook user is selling a bike,” for example. In that case, the only way someone can contact that person is by posting a comment and waiting for the seller to respond.

People who aren’t members of Facebook can see your listings by browsing and searching Marketplace, but they can’t post, comment or contact users. Unlike online marketplaces or services that can be used by anyone, Marketplace requires that users be members of the site to interact with sellers, which can be a downside. Plenty of people who aren’t on Facebook might not want to join the social-networking phenomenon just to offload the old couch gathering dust in the garage.

All user notifications — messages indicated in red at the bottom right of a Facebook page — will reflect friends’ activities in the Marketplace, unless you reset the notifications of the Facebook Marketplace app to not notify you. I suggest doing this, unless you really want to know about all your friends’ activities in Marketplace.

Four color-coded icons represent activities in Marketplace and are useful when reading lists of items at a glance: A green dollar sign represents Sell It and a red heart represents Sell for a Cause, for example. And details about each cause are integrated within Marketplace.

The Oodle-powered Facebook Marketplace is straightforward and well organized, and if you’re a Facebook user, its format will be familiar. If you’re not, and you’re looking for a way to sell or give items away for a charity or otherwise, Marketplace might encourage you to join the giant social network. But its payment program could be made a lot easier with electronic options.

Edited By Walter S. Mossberg

• Email us at mossbergsolution@wsj.com. Find this and other columns and videos online free at the All Things Digital Web site: http://solution.allthingsd.com

One welcome sign is an effort by companies trying to improve Microsoft Corp.’s (MSFT) Windows Mobile operating system, which has a reputation for confusing navigation and hasn’t had a major update recently. Kinoma Inc., for example, recently released an application called Kinoma Play that runs on Windows Mobile devices and gives users a markedly better way of handling photos, videos, music and Web browsing.

The HTC Touch Diamond, due out this month from Sprint, tries to hide Windows Mobile software.

This week, I tried yet another software program that is designed to run on top of Windows Mobile software. But this time, the software is at the heart of a device designed by the same company: HTC Inc. I tested the HTC Touch Diamond, due out from Sprint (S) sometime this month for $250 (after a $100 mail-in rebate) with a two-year contract.

Taiwan-based HTC started out in 1998 as a maker and designer of mobile devices for other companies. A year ago, HTC launched the first device under its own name in the U.S., and now, Sprint, AT&T (T) and T-Mobile (DT) sell HTC-branded devices. The Diamond incorporates HTC software, as well as software from Sprint, MobiTV, TeleNav and others. But it isn’t a stretch to imagine HTC trying to create a fully end-to-end model (hardware and all software) in the future.

The Diamond has a touch screen, but it’s smaller than Apple’s (AAPL) iPhone — 2.8 versus 3.5 inches. This screen lacks the iPhone’s multitouch functionality, and its smaller size robs space used for touch gestures like flicking or scrolling with a finger. Yet like the iPhone, it relies solely on an on-screen keyboard for all text entries. Even with the Diamond’s stylus, the keyboard felt small and cramped. Using just your fingertips was next to impossible.

After using the Diamond for a week, I can say that despite its handsome TouchFLO 3D software and animated icons like photos that flip from one to the next with a flick of finger, this device failed to disguise the frustrating interface of Windows Mobile often enough for my taste.

It reminded me of the brown paper bag book covers my Dad helped me make for schoolbooks when I was a kid: They looked great on the outside, felt sturdy and clean and created a blank canvas for homemade doodles that were often more interesting to me than the books they covered. But my book covers couldn’t change what was underneath; pages of frustrating algebra were just a flip away.

HTC’s sleek software tries to hide Windows Mobile, but menus from the Microsoft operating system are constantly popping up. HTC’s email program, for example, is represented by an animated envelope icon that, when selected, cleverly flips twice before sliding an email message half-way out and giving you a three-line peek at what’s inside. If only reading and responding to email were half as entertaining. Selecting the animated envelope opens the old, cumbersome Windows Mobile email program.

Also, the touch capabilities of the Diamond’s screen didn’t work as well as they should. Finger flicks that should have scrolled through lists instead seemed to select individual items in a list, as if they were sticky.

The Diamond isn’t all bad, of course. Plenty of people will like its smaller size because the iPhone and RIM’s (RIM) BlackBerrys seem too large and brick-like to hold up to an ear for phone calls. Next to my BlackBerry Curve, the Diamond was of comparable thickness but measured smaller in width and length.

Despite its size, the Diamond is packed with features. It has a 3.2-megapixel camera with autofocus that doubles as a camcorder, and comes with four gigabytes of internal memory and a removable battery. I taped short videos — something the iPhone can’t do — and found the sound and video footage to be adequate.

HTC touts the Diamond’s browser, which is based on the Opera browsing engine but is designed for HTC. It opens Web pages in views that fit the screen and text is automatically resized as users zoom in or out, though this resizing was sometimes slow.

Unlike the iPhone, Web sites that are opened on the Diamond’s browser don’t resemble the actual site as you would see it on your computer. I opened CNN.com (TWX) and WSJ.com (NWS), two sites that are packed with text and graphics on a regular browser. On the Diamond, they quickly were rendered in list format with mostly text-only. I easily touched the screen to follow links to full stories.

Like the iPhone, the Diamond has an accelerometer, though it’s called the “G-Sensor.” When it worked, this feature flipped the screen to match the horizontal or vertical direction in which the device was being held. Photos flipped instantly, but the Diamond’s G-Sensor took almost three full seconds to respond as I flipped from vertical to horizontal while using the browser. And some Web sites didn’t respond to the G-Sensor flips at all.

A special YouTube application developed by HTC was easy to find on the device and worked quickly. My videos were organized into categories for All, History, Bookmarks and Search, though this last category required using the finger-fumbling keyboard. In one step, I emailed a link from a YouTube video to a friend using the device, with a still shot from the video included in the message.

Overall navigation on the Diamond isn’t as intuitive as on the iPhone or iPod Touch, nor was it as easy as on a touch-screen Windows Mobile device running the Kinoma Play application. The iPhone and iPod Touch use quick double-taps on touch screens to zoom in or out, and multitouch capabilities resize images with pinching gestures; Kinoma Play uses a long touch to zoom in. The Diamond used double tapping on some screens, but not enough for me to grow comfortably reliant on it. A small, circular pad beneath the device’s touch screen provided a more dependable method for zooming in or out of screens: tracing the perimeter of this circle clockwise with a finger zoomed in; counterclockwise zoomed out.

The HTC’s software animation is put to good use on its Weather screen. Here, animated illustrations of each day’s weather appear on the screen: suns spin, clouds move in, rain appears to fall. Even moons appear on the device at night to accurately reflect the weather in a city at a specific time.

It is exciting to think about other mobile-phone companies giving better software a real try, especially those that attempt to improve Windows Mobile. But HTC’s Touch Diamond doesn’t hide the outdated operating system well enough or often enough for a user to want to buy a whole new mobile device.

Edited by Walter S. Mossberg

• Email us at mossbergsolution@wsj.com. Find this and other columns and videos online free at the All Things Digital Web site: http://walt.allthingsd.com