Soapi.CS is a C# wrapper with full coverage of the Stack Overflow API.
Soapi.CS is intuitive, fully documented and runs on .Net 3.5/4.0, Silverlight 3/4, Windows Phone 7 and Mono
For now, see http://stackapps.com/questions/386
for more info.
codeplex keeps messing up the repo and making it impossible to check in.