I don’t see this so much as a public site, but more about matching people up to share the drive to get better.
what did you have in mind? What form would it take? What technologies would it use?]]>
As for existing venues, doesn’t Flickr have invitation-only crit pools?]]>
Newstoday.com has a public feed where you can post work and ask for feedback in the discussion board.
BTW, I’m currently redesigning my own site and hopefully can get your feedback when it’s ready?]]>