These are the websites that I found the most useful whist trying to learn Unreal Script.

First of all the Unreal wiki has been endlessly helpful (though a bit difficult to find what your looking for at times)
Utilities for scripting in Unreal. The mutator FAQ was particularly helpful.
The UnrealScript API.
UnrealScript tutorials very helpful early on.
More nice tutorials.
Unreal Tournament scripting forum.
Unreal Developer Network alot of information about the "editable" aspects of Unreal.
Ask a coder forum.
My cry for help at the beyond unreal forums.