InviteShare - easy way to get invites for private betas like Pownce
It's the whole 'what you give, you keep' philosophy. Your email address will be public so that you can receive invites and send them to others. If this bothers you, at least InviteShare uses an image based email list to prevent spam.
Pownce was the invite in hottest pursuit, followed closely by Joost. The way it works is you add yourself to whatever private beta you're interested in receiving an invitation. Members who have invitations will click on your email image and press a 'sent invitation' or 'message' button. See screenshots below:
The site itself was somewhat confusing to navigate as it has no tabs. Your browser back button will help you out and hopefully InviteShare will add some much needed orienting features.
InviteShare has 42 private betas listed, some of which are:
Pownce, Joost, 8apps.com, Spock, moola, Grand Central, Gleam'd, iminlikewithyou.com, and more.
Btw, InviteShare was just bought for $25,000 by an anonymous donor. Sheesh. It was created and sold in just 4 days!
Update: We have learned the anonymous buyer is TechCrunch which just announced the news 7/19/07.