aSmallWorld
www.asmallworld.net
Numbers: About 130,000
Typical user: Jet-setters who surf the Net
The skinny: Founded by Erik Wachtmeister in 2004, aSmallWorld is an invitation-only digital Rolodex that lets members share travel tips and engage in online discussions on topics of interest. It has a global marketplace for conducting business away from eBay's huddled masses.
The site is not for everyone. To join, you have to be invited by a "trusted" member, i.e., one who's got permission to sponsor newbies. "If you have no friends who are members yet," the site explains, "you simply need to be patient."
And once you're there, you'd better play by a set of rules that discourages social climbing -- lest you be banished to a parallel community called aBigWorld, which lacks some of the features and exclusivity of aSmallWorld.
Raking it in: Advertising. aSmallWorld has hosted a gathering for members at the ritzy French resort St. Tropez, and acting president Nirav Tolia says the site plans to branch into additional ways that will enable members to meet offline. Future gatherings might also generate revenue for aSmallWorld.