Time to boost the signal! This September I am planning on doing a roundup of some favourite resources for Table Top Role Playing Games. Most of which are free and online.
Created by Keir (a.k.a. ProbableTrain), Dungeon Scrawl is a mapmaking program that lets you draw both top-down and isometric maps. I've been following it since Keir first showed an early demonstration of it on Twitter this past Spring. I have been using it since June. All but two of my published works use maps made with Dungeon Scrawl.
Here is what I have made with it, combined with Photoshop or GIMP: