PyMapper!

Tiled is a general purpose tile map editor. It's built to be easy to use, yet flexible enough to work with varying game engines, whether your game is an RPG, platformer or Breakout clone. Tiled is free software and written in C++, using the Qt application framework.

AutoREALM is a Free GNU mapping software (a "cartographer") that can design maps of castles, cities, dungeons and more. AutoREALM is generally used by Role-playing Game practicants who enjoy doing their own maps. But it could fits the needs of other people. If you are a Role-Playing gamer or else, you are cordially invited to join the AutoREALM community: fellows gathered around a free hobbyist map tool. Originally made by Andrew Gryc (say "grits"), AutoREALM is now Open Source, creating a unique opportunity for the RPG world to mix graphics and computer programming. »

Campaign Cartographer is the leading map making software for games (RPGs, miniatures and wargaming). Campaign Cartographer gives you fingertip control of both the big picture and the small details. Want a large scale map of your adventuring world? A detailed dungeon floorplan? An historical battlefield littered with burnt-out tanks? CC3 can deliver all of this and lots, lots more.

Dundjinni is a full-featured fantasy map creation program. It allows users to create walls and floors, place objects, insert text, and more. It boasts an intuitive interface and an impressive selection of objects and textures (over 190 images). It also allows you to author d20 adventures in a simple yet elegant way.

With Fractal Mapper, creating worlds has never been so easy! Fractal Mapper is a high-powered mapping system that lets gamers create a wide variety of of maps - dungeons, continents, cities, and more! With it's easy to use interface, powerful features, and unique capabilities, making high quality maps with Fractal Mapper is a breeze!

From Wizards of the West Coast, the Dungeon Tiles Mapper lets you create tiled dungeon maps online for free through your browser using a simple grid-based editor. Just select your tiles and drag them where you want them.

Tiamat is Web 2.0 Tile Mapper; Ideal for creating miniature scale maps for role playing and miniature games. Tiamat is FREE to use to create maps. You only pay for the maps and tiles you want exported for personal use. The software is still in beta.

Old but still popular, ugly but powerful.

Hextml is a web-based map maker and campaign manager. It uses the best of HTML5 to let you make beautiful hexagonal maps. Maps can be linked together with submaps to design some location with more details. Custom tiles can be imported into the software.