Members: 320,000

Perks: Chit chat with the ultra-rich on the site's forum about the best hotels in Monaco, buy a yacht from a member on the Market Guide, scour the luxury travel guide or browse the social calendar. This is by far the most active and well-known exclusive social networking site on the web … but competition is biting its heels.

Getting in: Members, who pay no fee, induct newcomers on the basis of education, profession and their network of contacts. If you don't know a member with invite powers, you're out of luck.

Diamondlounge.com

Members: 150

Perks: Modeled on real-world club Studio 54, the site is moving away from its initial emphasis on social and business networking and focusing more on dating and fun, according to owner Arya Marafie.

Getting in: Potential club members can apply online and will be accepted or declined based on what they do and whom they know. A $50 monthly fee is expected to keep out the riffraff.

Squa.re

Members: 600; 10,000 page views a month

Perks: Want to see behind the velvet ropes at the hottest club in London or who attended the Marc Jacobs post-show party in New York? Or do you want to show off which A-listers you mingled with last night? Squa.re features community-generated Internet TV focusing on nightlife, style, high living and luxury travel. Each video or photograph uploaded by members has to be approved by the Squa.re staff for quality and class.

Getting in: E-mail Squa.re and request an invite if you're a trend-setter in (or even remotely connected to) one of the network's four channels, but getting your user-generated content featured is more challenging.

LuxuryRatings.com (launching in May)

Perks: Unlike other exclusive networking sites, this one won't be 'chatty,' according to the Luxury Institute's CEO Milton Pedraza. It will be a network of member-generated ratings for brands and the people behind them. So if you're looking for an art dealer, financial adviser or wealth broker with a recommendation from like-minded wealthy peers, this could be the place to go.

Getting in: $250 annual fee.