My Favorite Wiki: pinvoke.net
I guess wikipedia is cool, but the wiki that provides a vital service in my life is pinvoke.net, which provides an enormous, user-contributed list of Win32 API mappings for .NET. I find it useful not just because folks are contributing tons of stuff I use, but also because I find it a wonderful place to drop code for my own later use, e.g.
This is the closest thing I’ve seen to a working code repository that is just as easy to contribute to as it is to use. Highly recommended.
P.S. I think this kind of functionality should be built into the SDK docs. I’ll ask ’em.