here are some useful tools I used in the past to work with Unreal packages and UScript.
WOTgreal Package Exporter
This old and well-known tool allows exporting of classes, meshes, textures and sounds from unreal packages. Very useful if you plan to get textures and sounds quickly.
http://www.wotgreal.com
UTPT
UT Package Tool can be used to analyze packages of many Unreal Engine 1 and Unreal Engine 2 games and to export data from them (UT3 packages are not supported).
UTPT can list all stuff contained in a package. GoPo loves it !

http://wiki.beyondunreal.com/UTPT
ChocoPackageEdit
As UTPT, it can read unreal packages, it lets you give a full-depth look into the UScript code...
UE Explorer
It's a recently new software, a powerful UnrealScript decompiler for Unreal Engine packages from Unreal, UT99, UT2004 and UT3. I think this tool deserves to be picked out

http://eliotvu.com/portfolio/view/21/ue-explorer
cheers,
Pietro