Assuming you know about using the load button while browsing textures to load up .utx packages of textures, I can point you to Planet Unreal>Texture Forest on left side. As for others they are scattered on user sites all over the place so you need to search a lot. Remember that you can convert any graphic to .pcx (8-bit) format and Import it into UnrealEd to use as a texture. See the Texture docs at Tech Pages (http://unreal.epicgames.com) for info. All textures must be sized in multiples of 2. For example, 128x32, 256x256(typical), 64x32, 12x18(avoid stuff like this). Multiples of 8 or 16 are really the best actually. Maximum size is 256x256 so chop up larger textures into pieces if you have to.
The best way to dig up resources is to click through to user sites but it takes up a lot of browsing time. In the end though you have a good idea of who has what and useful bookmarks.
