PyMapper - Drag and drop tile based mapping program.
Tiled Map Editor - Tiled is a general purpose tile map editor.
Fractal Mapper - With Fractal Mapper, creating worlds has never been so easy!
Tilesetter - The tileset designing software.
Tiamat - Tiamat is Web 2.0 Tile Mapper; Ideal for creating miniature scale maps for role playing and miniature games.
Inkarnate - A free-form map editor for role-playing games, focusing on overland and continental maps.