Netscape co-founder Marc Andreessen, Charles River Ventures and SoftTech VC have bet $3.5 million on SocialMedia Networks, creator of an ad and analytics network for widget makers on social networks like Facebook and MySpace.

SocialMedia, based in Mill Valley, California, was hatched by four co-founders, including Seth Goldstein, the chief executive, and David Gentzel, vice president, products.

The funding comes as venture capital investors seek business plans for spinning profits out of widgets, small programs that deliver features while riding the back of social networks.

SocialMedia was formed earlier this year with help from Charles River Ventures, which provided a loan through its QuickStart program that converted to preferred stock with the A-round financing.

Another venture firm, Bay Partners, based in Menlo Park, California, has launched an “AppFactory” to fund creators of widgets for the open Facebook platform.

News Corp.-owned MySpace, the most heavily trafficked social network, has announced plans to follow Facebook in opening its system to third-party widgets as well.

Mr. Andreessen, a new investor in SocialMedia, gained fame for his role for developing the Netscape browser in the 1990s and later as an entrepreneur. Ning, a company he co-founded, offers a platform for social-networking web sites.

Mr. Gentzel is the developer of Trakzor, a widget that lets users see who has visited their MySpace profiles. Launched in May 2006, the widget picked up 4 million users by April, when the 24-year-old Virginia Tech graduate moved to Mill Valley to join the SocialMedia team.

Though SocialMedia has developed a popular FoodFight widget, which lets users throw food at each other in cyberspace, the company moved to build tools that would help applications developers.

"Widgets themselves are a hit-driven business," Mr. Gentzel explained.The company’s Appsaholic program lets developers track the activity of Facebook widgets and creates an ad network around them in a social-networking version of Google’s Analytics and Adsense.

“Every social network potentially could become a platform,” Mr. Gentzel said. “Right now in Facebook, we serve at least 150 developers. It seems over the last two years, any consumer-facing site has a widget.”

George Zachary, a partner with Charles River Ventures, said SocialMedia would use the funds to continue development.

SocialMedia “will use these funds to develop its tools and services to become the first and largest application network,” he said in a statement.