Inkarnate - A free-form map editor for role-playing games, focusing on overland and continental maps.
Campaign Cartographer - Campaign Cartographer is the leading map making software for games (RPGs, miniatures and wargaming).
PyMapper - Drag and drop tile based mapping program.
Wonderdraft - is an intuitive yet powerful fantasy map creation tool for 64-bit Windows 10, Linux, and MacOSX.
donjon.bin.sh - Freely accessible online collection of random generators for tabletop games.
Dungeon Tile Mapper - Dungeon Tile Mapper is a web based tile mapping tool that includes many official D&D tile sets.