Before web services go ‘public’ they hang around in ‘beta’ mode for a while.Â Often while in beta they are by invitation only.
A site (such as gMail was and Pownce currently is) often helps to build hype – people go hunting for invitations to said sites and those lucky enough to have invitations try to cash in while they can (sometimes they even sell on ebay).
InviteShare.com is a place to share and request your beta invitations. Those people needing invitations can add themselves to the appropriate application request list and those with invitations can browse the appropriate invitation list, send invitations and mark the user as ‘invitation sent’.
There are currently 31 sites listed on the board.
It’s worth taking a look.