RegExLib has good repository of user submitted regular expressions. For each expression, other users are allowed to make comments so there's some collaboration and feedback on what people submit.
I'm not sure how big the community is for the site, so I don't know if submitting your expressions will guarantee feedback, but I've found it to be a good starting point when I've needed a starting point for developing some expressions.
The site also has a great regex tester, which I have found to be a very valuable resource when developing and testing my regular expressions.
You mentioned having a "website where anyone can edit (like a wiki) or within a team."
Why not see if you can get a spare computer, setup your own open-source wiki, and run your own site for your internal team. An old desktop running under your desk would probably be able to handle the load for your team. And if it was getting enough use to need a better computer, well that would be good proof and justification to your manager or whoever that it actually is a good resource for the team and deserves better hardware. (even a sharepoint site would work instead of wiki if your company's has restrictions on what you can run. I worked for a mid-size company where there was some strange bureaucratic dispute over wiki vs. sharepoint because someone thought it would be a good idea to be consistent. totally dumb.)