idproxy.net is a spanking-new service that lets people use their Yahoo! identity as an OpenID. Yahoo! released the API for their BBAuth service last fall, but it doesn't support any of the existing identity standards. So idproxy.net uses BBAuth to allow users to authenticate, and then use that identity to create OpenID URLs in the idproxy.net domain.
I think this is a great idea -- I'm bitterly jealous that I didn't think of it. I've been experimenting with BBAuth since it came out, and I've wanted to make a plugin for MediaWiki that would use BBAuth to allow Yahoo! users to log into Wikitravel, but at this point I don't think I'll bother.
Simon Willison has more info on his motivations for starting idproxy. Good luck to him.
tags: idproxy openid simon willison yahoo bbauth