You can't mod the game as EVERYTHING is server side. There are some tools that allow you to make and test character builds like the ones below.
Anything else you see that claims to allow you to mod or edit or anything else like that is probably a key logger.
The Edge V2.0
GW Manager
No Customer UI's yet but the fans have been asking for ages for ways to customise your UI beyond what you can do at the moment in your options screen.
For example my UI looks like this.
Basically I changed where the Monster HP, skills and skill activation bars are to make it easier to see without my eyes also leaving my HP and Skills.
It is against the EULA and ToS for you to mod the game unfortunately.
[ 08-19-2006, 09:28 PM: Message edited by: T-D-C ]