Baron,
Take a look at this then...
http://uaf.sourceforge.net/
Dungeoncraft, guy from scratch is reproducing Unlimited Adventures, the D&D computer game construction kit.. I had a blast redoing a couple of old TSR modules (I loved Village of Homlet for some reason!)
Also, as a world builder, you ought to be excited about NeverWinter Nights.. Its made so that new worlds can be created quickly and easily. I was reading in an interview where they mentioned the only tools they used that you dont get with the game are StudioMax and Visual Studio...