Ask the average sports fan to tell you about Web 2.0 and he’s likely to wonder whether you’re talking about an obscure statistical category. But through message boards and fantasy games, millions of them have been unintentional Web 2.0 participants even before the moniker existed.

Now, sports sites are turning to blogging and social networking as a way to engage fans and score marketing points.

The applications run the gamut. Sporting News magazine’s site is heavy on reader comments and user-created blogs. Sports Illustrated recently partnered with Takkle.com, a social networking site where high school athletes can post highlight videos to gain exposure to college recruiters.

NASCAR.com launched a community section last month that’s squarely in the wheelhouse of the auto racing circuit’s rabid fan base. And in an ambitious move, the Indianapolis Colts are preparing to launch MyColts.net, a MySpace-like, Colts-themed social networking site.

According to Hitwise click-stream data, 8.58 percent of the traffic to NFL.com in January came from MySpace, while 13.02 percent of the traffic to nba.com for the same month came from the social networking giant. While it skews young, MySpace clearly attracts a diverse audience of sports fans. “What it’s telling [sports marketers] is that social networking is a very significant traffic source,” say Bill Tancer, Hitwise’s general manager of global research.

MyColts.net and NASCAR’s Infield Community will facilitate blogging by offering tools and artwork. The Colts created an application that fans can place on their profiles. Pat Coyle, the Colts’ director of database marketing and e-commerce, says the team envisions MyColts.net as a versatile way of connecting with fans.

“We’re expecting sub-groups to form and niches to emerge,” says Coyle, adding that about 7,000 fans had preregistered with the site. “The more we know about their interests, the better we can serve fans and keep them engaged in the community, the brand, and buying tickets. In turn, we can sell to sponsors what we know about people to help them position brands.”

A social networking site seems like a perfect fit for NASCAR and its notoriously passionate fans. But there could be a point of diminishing returns as more social sports sites emerge. “How many social networking sites is a person willing to reckon with?” Tancer wonders. “Imagine a world where every team or sport created their own. It would be too fractional to get traction. The smarter play may be to consider leveraging existing social networks.”

For example, Tancer pointed to 20th Century Fox, which promoted the film John Tucker Must Die from within MySpace by creating profiles of the characters. “It was a brilliant way to take a marketing initiative and get people involved,” he says. “In sports, there’s the same potential. Maybe you take top personalities from your team and integrate them within a social network setting.”

Michael Adamson, vice president of new media for Turner Sports, which produces NASCAR.com, says fans have been asking for ways to get involved other than participating in discussions: “We don’t believe that online socializing is yet saturated, particularly for a community that is based on a specific interest, such as NASCAR.” He adds: “We believe this is a great opportunity to engage fans in something new that they can relate to. We expect people will jump into social networking for the first time because of this.”