Google SketchUP is a free 3d tool (there is a pro version, but the free version is pretty functional by itself) that can be used to make simple 2d drawings "come alive". SketchUP can be found here:
I didn't fully understand just how useful it could be for rpg maps until I came across a series of threads by a user named None the Wiser on the Goodmangames messageboards.
Go to the forums (http://www.goodmangames.com/forum.htm) and look in the "art & artists" subforum near the bottom of the forum listings. None's threads should be near the top in the subforum and check out the 3-D Wildsgate Excursion thread (based on maps from a DCC module). Incredible--I'll never look at towns and the old classic dnd "overhead" map quite the same way again. His Sunken Ziggurat thread is pretty amazing as well.