Super simple map-making tools

Sometime back I went looking for a simple map-making program for drawing out a loose view of areas either for a home, apartment, or a Dungeons and Dragons campaign.  I'm not pursuing this track any longer but I spent enough ours looking around that I decided I'd list out some possibilities:

• RPG Boss (open source, might be portable)
• Tiled  
• Other RPG Creation software (wikipedia)

I had some success once upon a time with Paint.NET (not portable) zoomed in with the "Grid" settings enabled but not much more.

Related: a portable tool for real map management