Top 5 Niche Social Networks

2 is a Web site that connects current and former classmates. It was one of the first social networking sites, launched in 1995. Basic usage of the site is free, allowing users to search for and view alumni from their high schools or colleges. However, users must upgrade to a paid "gold" membership in order to view people's details or send them a message.

The alumni network currently has 4.6 million paid users and 40 million registered accounts [source: Tartakoff]. The site is popular with people trying to set up class reunions or find out contact information for classmates they've lost touch with. Users can set up a profile with their high school or college and graduation years, which will make them searchable to other people. The site features message boards where classmates can share information about other alumni or plan a reunion. also features "interest groups," where users can connect on a variety of topics. People network with each other in forums about business and the workplace, the military or sports -- just to name a few. A message center helps users contact each other without being forced to give out their personal email addresses.

In a time when a free social network like Facebook is exploding, some people wonder if is about to go the way of the dinosaur. However, -- a niche site, unlike Facebook -- continues to pull in both members and money [source: Tartakoff].