A few places.

 

Check out the MSDN Library.  Along with the API, it has a lot of good references and tutorials.

http://msdn.microsoft.com/en-us/library/default.aspx

 

If you can't find what you need by doing a Google search, you can always just ask here, or on the MSDN or CodeProject forums:

http://social.msdn.microsoft.com/Forums/en-US/categories

http://www.codeproject.com/script/Forums/List.aspx