Indie-Resource.com

So while doing a small google search, I found this thing... It is used to create maps for fantasy worlds, dungeons etc... Sadly you have to pay to get it... But the demo version is worth taking a look at.
http://freefantasymaps.org/

Ahhh yes, Campaign Cartographer. I have it

However, I really should check to see if they have updated it to work better with post-Vista versions of Windows. It was very, very glitchy last time I used it a few years back, even using compatibility settings.

Have you checked out Tiled? I'm not very good at making maps but I tried this one and kind of liked it.

Campaign Cartographer is really different than a tile map editor. CC3's original purpose was for making printable maps for pen'n'paper RPGs, but some have found it useful for making video game graphics. Because of its past, it works very differently to a tile map editor. You first basically draw a background, and then you add entities to the map to flesh it out. For usage in a video game, you may still want to cut it up and create tiles with it, which could be done by Tiled.

I have a copy of this as well. Somewhere. Good software, especially for Pen and Paper RPG development.