I found these sites EXTREMELY helpful when I first started out building UT maps. If you are interested in creating your own UT maps and are new to UnrealEd, use these sites, because they are excellent resources. And a word from someone who has been there before: It may be hard for you in the beginning, but don't give up! UnrealEd may seen complicated, but once you get used to it this program is very easy to use and is really dynamic. Once you learn how to use UnrealEd, the sky is the limit.
UnrealEd.exe- Absolutely awesome site to find all information on using the editing tool. If I am really stuck on something this is the first place I turn to. http://www.planetunreal.com/unrealed/
UED Lab- Another cool site with tutorials and some helpful utilities. http://www.planetunreal.com/uedlab/.
Weapons of Destruction- A really cool site for those of you who want to make your own weapon mods. http://www.planetunreal.com/wod/
Prefab Central- Nice place to get your prefabs if you don't find what you want on my site. http://www.planetunreal.com/wod/
Prefab Lab- Another good place to get your prefabs. http://www.planetunreal.com/prefablab/main.asp