Right now I use Corel Draw.
I have all the pieces I own in one drawing that I can quickly arrange.
Then I print that map off before play and can build the map on they fly as we play. (Plus my players enjoy placing the pieces and helping out)
If your Local store carries it, I would go that route, if it is cheaper.
I got mine from the WOTC store here in Grand Rapids. They were actually $10 lower than the suggested retail price. I got the cavern set for $89 (it is supposed to be $119). I am think of possible picking up another one of those for my birthday (if I can sneak it past my wife)
Hey, if anyone wants my Corel Draw file, it is on my website (though my ISP is sometimes flakey, and I have to reset the DNS, but It is normally up) Check under the Gaming Resources, then the DND Resource. I also have a few sample maps there too.