I've come across Code Golf, where golfing challenges can be solved in 4 different languages: Perl, PHP, Python and Ruby.

The site is quite young and the "interface" is still evolving. At the moment it's not possible to see solutions to older challenges (none of them is actually closed), but I've read that they're changing the basic rules to have "golfing seasons" (here's the relevant post).

An overall leaderboard of languages is also missing. At a first glance it seems that the shortest solutions are either in Perl or in Ruby: I hope some good monk will put it right :)

Update: corrected link.