BirdForum Opus

BirdForum, the very popular birding message board, has launched its "Opus". This site is a wiki-driven encyclopedia of birds, bird song, birding/photography equipment, and birding locations. I browsed through it briefly and I found that it's filled with a lot of great information on birding worldwide. There is an entry, or at least a stub, for all the birds of the world. The location section is heavily European right now, but that's to be expected since BirdForum is a European site.

There is also WikiBird, another Wiki birding site. It doesn't seem to have as much information as the Opus and seems to be more US-focused.