People are popping up all over on Facebook like so many prairie dogs in a Kansas field. The social networking site has been growing at lightning pace. It now has more than 64 million active users and has had an average of 250,000 new registrations per day since January 2007, according to its statistics page.

It didn't take long for eBay and online sellers to spot the opportunities on Facebook (http://www.facebook.com), especially on a site that has "networking" in part of its name. Although the site has only just started exploring out-and-out advertising, there are many ways for Facebook users to get the word out about their wares. (And it's easy to have fun while you're there, especially for a site rife with fluffy little apps like "Happy Hour," where you can send a virtual drink to your friends, and a quiz naming car logos of the world).

News Feeds
A "News Feed" shows up in the middle of your Facebook home page, informing you what is going on with your Facebook friends. For example, the feed may notify you when a friend joins or leaves a Facebook group, adds or removes an application (see below), or comments on a photo.

You can also use the "Status Update" feature, which allows you to write a short note about what you're doing or thinking that moment. This is also a good way to alert your Facebook friends if you've made a new blog post. You can also add a Feed or Blog application to your page to keep folks piped into your blogging activities.

Applications/Widgets
Facebook offers a number of widgets, aka "apps," which allow you to embed a little mini-program within your profile on the site, publish news stories that go out to your friends, etc.

For example, the "eBay Marketplace" app lets you broadcast to your Facebook friends when you sell an item on eBay, and they can click a link to see what else you are selling.

The "eBay to Go" widget lets you choose from several versions - a "single item," "multiple items," "search," "seller," and "store."

And Apps go beyond eBay as well. There are other ecommerce apps to choose from, such as these (you must be signed in to Facebook for the links to work):

My Etsy: http://apps.facebook.com/myetsyapp

Garage Sale: http://apps.facebook.com/garage_sale

Facebook Classifieds: http://apps.facebook.com/garage_sale

Groups
Aside from marketing to your friends with the widgets, you can join a "group" of like-minded people on Facebook. There are a number of eBay-related groups: including "addicted to eBay," with 2634 members at this writing; "half.com by eBay," with 2,059 members; "$$eBay addicts$$," 567 members; "Facebook eBay," 212 members; and so on.

One way people market using these groups is to post notes, including their eBay Store links, to its "Wall," or discussion board.

In the "Facebook eBay" group, people are using the wall to post about their blogs and websites as well as their eBay stores. "I've just got my first sale on my new website...yipeeeeeee!" posts "Kate" from the UK. Others are grumbling about the new fees and feedback policies.

"Gardell" from Raleigh/Durham, NC, posted a link to his eBay MyWorld page, and "Lior" in Israel posted a link to an eBay Guide he wrote about how to tell which Sandisk memory cards on eBay are fake.

Posting a Video
Perhaps more effective than posting a simple note or link to a group is posting a video. Fewer people are doing it, and a video has more staying power. But make yours informational and not just an out-and-out commercial.

Juergen Horn, co-founder of www.LastMinute-Auction.com, posted such a video to the "Addicted to eBay" group, titled "Find Bargains on eBay." It's a clip of a tv story the BBC did about finding bargains on the lastminute-auction.com site, which lets users browse up to 30,000 eBay auctions at one dollar and with only one hour left. Horn says he posted that video to various eBay-related groups to promote the site.

But it's not just eBay groups you should be thinking about. eBay powerseller and author of "The Stay-at-Home Mom's Guide to Successful eBay Selling" Suzanne Wells, who writes a blog at PowerSellerKing.com, advises that you "join groups that relate to your product line on eBay."

Wells' main product line is golf apparel. "I seek out groups that discuss golf techniques, golf clubs and equipment, golf vacations, golf news, golf history, golf tournaments, famous golfers, etc.," she says. "If you have a presence with your target market, you'll have a better chance of making more sales."

eBay seller Jon Barber (http://members.ebay.co.uk/ws/eBayISAPI.dll?ViewUserPage&userid=barspeed1975) uses this approach as well. "I market my brickabrack through letting friends know at forums I use; the items I list are therefore aimed at a specific group of people and more likely to sell. I tend to list an eclectic mix of items - people often put me down as a favourite seller, and I often sell to the same people," he says.

Wells says you may even want to start a group that pertains to your product. "For example, if you sell movies on DVD, you could start a movie discussion group. If you sell designer clothing, start a fashion group and discuss fashion trends, celebrity fashion, fashion dos and don'ts, etc." But she cautions that "blasting on the scene and announcing "buy my products" will not work: You must be delicate and subtle when approaching potential customers and create a trusting relationship first. Gain their interest, offer helpful information, be professional, and the sales will come."

Facebook Ads and Pages
You can also run pay-per-click ads via facebook's Social Ads program, or set up a free business page with Facebook Pages. Horn says the best results he's gotten have been "using facebook's ad marketplace, where you can bid on keywords traded at a specific facebook user group." But you certainly don't need to spend money to attract attention. "As for free traffic from facebook," says Horn, "my guess is that around 50 or 70 every day will find their way from facebook to our site."