Just wanted to point out a new online tool Dwarven Forge has released as part of their Game Tiles Kickstarter project. It’s a mapping tool using the various pieces that come from the Kickstarter. But there’s no reason you couldn’t use it as a quick-and-dirty map-maker for any game, even if you have no plans to use their game tiles. It’s fairly versatile considering its simplicity, allowing for even diagonal corridors. Unfortunately, it’s limited to just 2-sets worth of tiles, but hopefully that shortcoming will be addressed in future updates.
Here’s the link if you’d like to try it out: Dwarven Forge Map Maker