Here's a neat little tool for all of you playing tabletop RPGs online: Dungeon Scrawl, a piece of free mapping software that's pretty simple to learn and has a bunch of presets that make maps look great in a variety of styles. It's not much harder to use than, say, MS Paint or the like, but gives results well beyond most other free programs I've encountered. Presets generate your modern-classic dungeon maps, complete with crosshatching at the edges, or a retro-TSR blueprint look, or maybe a sci-fi orange and black.
I'm a big fan of the variety of brushes and tools in the program as well. Being able to easily copy-paste and paint in new areas is nice. Want a cave that's 50 feet across, but has jagged edges? Easily done. You can also do things that are a pain in other programs, like rotate rooms while ensuring that corridors line up, very easily. You can also import maps from popular random dungeon widgets like Donjon or Random Dungeon Generator to get a simple start on your maps. What really seals it for me is that the tool has both standard and isometric edit modes. Isometric maps made easy! Your infinity engine RPG fantasies can come true!