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

When the moment comes to take the perfect picture of a snowy mountaintop, Fourth of July fireworks or soccer goal in midkick, most people forget about these features or don’t know how to use them. And while many digital cameras can now detect faces and make sure they are in focus, they can’t tell whether that face is smiling or not. The results aren’t bad, but they could be much better.

Sony’s Cyber-shot DSC-W170 uses Smile Shutter Mode to snap pictures when a subject smiles.

This week, I tested three new digital cameras that claim to do the thinking for you. Some digitally analyze the scene you’re about to capture, automatically choosing the setting that would take the best picture. Others can detect when a subject is smiling so as to automatically know when to snap the photo. One camera even attempts to digitally alter frowning faces into smiles, with amusing results.

I tried out Sony’s $300 Cyber-shot DSC-W170, Kodak’s $250 EasyShare Z1085 IS and Olympus’s $200 FE-340. Only the Sony (SNE) includes all three of the aforementioned features; the Kodak (EK) has scene detection, and the Olympus (OCPNF.PK) camera has built-in smile detection. I found the automatic scene detection offered in the Sony and Kodak cameras to be the most useful feature for everyday photos. It improved my photos and didn’t require any extra adjustments. I handed the cameras to other people to take pictures, without having to change any settings.

The automatic smile detection offered in the Sony and Olympus cameras was fun to use and could be especially helpful for families whose young kids never seem to smile at the right moment. But it didn’t work consistently and had trouble detecting my bearded boss’s smile and even that of a beard-free colleague.

I found Sony’s frown-fixing tool, which is called Happy Face Retouch, to be rather unusual. It took already captured images of my friends’ faces and turned their frowns or ambivalent looks into smiles, but didn’t adjust the subjects’ eyes. Though this was good for laughs, the eerie-looking grins pasted on faces reminded me of painted-on clowns’ mouths. And some attempts to retouch a face couldn’t detect the face to alter it. But a handful of the Happy Face Retouches looked somewhat natural.

Similar Specs

These cameras boast many similar specifications. All three use 5x optical zoom lenses, and the Sony Cyber-shot DSC-W170 and Kodak EasyShare Z1085 IS each have 10.1 and 10 megapixel image sensors while the least expensive Olympus FE-340 has 8 megapixels. The Sony and Olympus both have generous 2.7-inch viewing screens and almost identically sleek builds, though the Sony is the only one of these three cameras to have an optical viewfinder.

The Kodak’s viewing screen is slightly smaller than the other two digital cameras, measuring 2.5 inches, but its build isn’t nearly as compact as the others. It reminded me more of small, high-end SLR camera, with its comfortably large hand grip, a settings knob on the top edge of the camera, and a protruding zoom lens.

Sony’s Happy Face Retouch feature digitally changes facial expressions into smiles, but all it did was make me look unnatural and awkward.

Kodak’s EasyShare Z1085 IS takes Secure Digital (SD) memory cards, which are more common than the Memory Stick and xD cards that work in the Sony and Olympus cameras, respectively.

The Kodak and Sony digital cameras have different names for their automatic scene-detection features. By default, the Kodak camera works in Smart Capture Mode, which includes intelligent scene detection, capture control and image processing. I focused on the camera’s scene detection, which automatically determines whether the photo should be taken in Macro, Text (for shots of text in a book, for example), Face, Landscape or Night settings.

Icon on the Screen

I snapped pictures around Washington, D.C., noting a tiny icon on the camera’s screen that indicated which of the five scene modes was being used to capture the photo. A flower icon indicating Macro appeared on my screen when I stooped to get a close-up shot of a tulip, and an icon of a dark sky and stars showed on the screen when I took photos at night. The camera’s flash, focus and exposure changed according to the type of photo.

The Sony camera uses what it calls Intelligent Scene Recognition to decide which settings should go along with certain photos. Like the Kodak, icons on the Sony’s screen indicated the scene settings that were automatically deemed appropriate, including Backlight, Backlight Portrait, Twilight, Twilight Portrait and Twilight Using a Tripod.

The Sony’s Intelligent Scene Recognition isn’t on by default like Kodak’s feature. Instead, it must be turned on from within a menu, but once on, it stays on until you turn it off. ISR can be used in either Auto or Advanced mode; Auto takes a single photo with automatically determined settings, while Advanced takes two shots — one with manual settings you can choose and another shot immediately following the first with automatic settings according to what the camera thinks is best.

I experienced surprising results with the Sony Cyber-shot DSC-W170 and Olympus FE-340 while testing their automatic smile-detecting functions. My friends thought I was joking when I told them the camera would take their picture only if they were smiling. When the flash went off multiple times as they kept smiling, they were intrigued by this feature.

Sony’s version, which it calls Smile Shutter Mode, is easy to switch into by turning a dial on the camera to a smiley face. Once this setting is chosen and the camera’s shutter button is pressed, the Cyber-shot will search for smiles in its subjects, and will take photos whenever it detects a smile. Settings within this mode can be set to specifically detect an adult’s smile or a child’s smile, and the degree of smile can be set to low, medium or high; I kept things simple by leaving the smile detector on default settings.

Capturing Smiles

Olympus calls this feature Smile Shot, capturing three rapid shots in a row to make sure everyone’s smiling. The idea of taking three shots would be extra helpful with an indecisive baby, but most of my friends were able to hold their smiles, which produced three almost exactly identical shots each time someone smiled. Smile Shot is harder to get to in a pinch compared with the Sony: it’s buried in a list of 13 settings on the Olympus when the camera is set in Scene mode.

The Olympus seemed to be a bit slower than the Sony when it came to detecting smiles, but both had trouble with bearded men and even some folks without beards. And people felt silly standing around with a smile on their faces waiting for the camera to finally work. Closed-mouth, no-teeth smiles were harder for these cameras to detect, but not impossible. In group situations, the Olympus camera will focus on whoever’s face appears largest, which could mean the person closest to the camera, while the Sony takes a picture whenever anyone in the group smiles.

Putting a Happy Face On

If someone isn’t smiling, Sony’s Happy Face Retouch tool can come in handy, but don’t count on liking the results. In a group shot of five friends, two people who weren’t smiling put a bit of a damper on the whole shot. I used Happy Face Retouch, but it picked up on only one of the nonsmiling faces, turning a confused look into a smile that looked passable. But other results weren’t usable. A serious-looking shot of me deliberately not smiling looked freakishly unnatural after the touch-up, mostly because the rest of my face didn’t join the smile. I looked more like someone who had received too many Botox treatments.

Sony says that, in group shots, it can detect and change up to eight faces, but in my tests it usually changed only one. This retouching tool is also difficult to find: It took me 16 button presses to change each image into a smile — or what Sony calls a smile. A few times, Happy Face Retouch couldn’t identify a face in the photo, even when just one person stood in the frame.

These digital cameras took good photos, overall, and are fun to use because they take pressure off the photographer. I found the automatic scene-detection tools of the Kodak and Sony to be the most realistic and useful offerings, and I’m sure it won’t be long before automatic scene detection becomes as commonplace as an automatic flash.

The chart below compares features of the three cameras described. Click on it to make it larger.

• Email mossbergsolution@wsj.com