Look who's making money on Facebook

Facebook now has 500 million users -- and thousands of companies trying to cash in on them. Here are four who have cracked the code.

This brand marketer uses Facebook to build buzz for its clients, which range from solo bloggers to megabrands like Coca-Cola. The goal is to win "fans" who, with one click, opt into further interaction with the advertiser.

Wildfire rummages through its bag of tricks to build marketing campaigns that include contests, coupons, quizzes and virtual gifts. The Holy Grail, says co-founder Victoria Ransom, is to get a campaign going viral. That spreads brand recognition like, well, wildfire.

"Companies can really benefit from viral channels, but not all of them have the expertise to do that," Ransom says. "At Wildfire, we know what works and what doesn't."

But the company isn't a traditional marketing agency. Its online system lets advertisers build their own campaigns, with rates starting as low as $5 up-front and 99 cents per day after that. Premium and white-label services are available for marketers with bigger budgets.

Greg Bettinelli of HauteLook, a designer clothing sales site, used the app to create a co-promotion contest with cosmetics maker Smashbox. "Every day we're rethinking the strategy behind connecting with our customers," he says. "It used to be: How do I get a discount code in someone's hand? Now it's all about how to extend that conversation into something meaningful."

Based in Palo Alto, Calif., Wildfire launched in summer 2008 and won a grant later that year from the Facebook Fund, which offers seed financing to promising ventures. Ransom says Wildfire reached profitability "very early on," and is planning to expand beyond Facebook into several additional social media sites. It's already doing some work around Twitter.