If you want to win friends and influence people, social-networking Web sites such as Friendster, Ryze, and LinkedIn can help you do it at Internet speed. These sites typically allow users to create online profiles, then build "personal networks" by linking to the profiles of friends or associates. Their friends and their friends' friends then become potential collaborators, employers, or dates. It's one of the hottest crazes on the Web, supplementing e-mail, blogs, and personal ads as a way to make connections.

Limiting the utility of online social networks, however, is the fact that one site's members can't connect with another's, so people who want to use more than one site must build separate networks. "Being able to connect the various presences you have in cyberspace is key," says Marc Canter, CEO of San Francisco-based Broadband Mechanics. He's talking with Tribe.net (also of San Francisco) and other companies about building a giant network of social-networking sites that would allow users to cross site boundaries.