Levels4you.com Lots of stuff to download.
DisastrousConsequences Rpg Invasion Server running Druids RPG and some other mods/muts.
Skin City
UT 2003 Headquarters More than UT2003 there.
3dBuzz.com
Psyonix Onslaught creators
Unreal Developers Network
Unreal Wiki Lots of tutorials here.
UT2004 UV Textures a forum post linking to d/l.
The book on Unreal also you can save alot of money getting books there.
Polycount