MapForge is described as 'Map-making software for creating tactical-scale battlemaps for RPGs (or even some boardgames), with a large library of ready-to-use mapping content Add-Ons (including 10 free ones!). Also works with your own artwork/bitmaps, via drag-and-drop'. There are more than 10 games similar to MapForge for Online / Web-based, Windows, Mac, Linux and Self-Hosted solutions. The best alternative is Tiled Map Editor, which is both free and Open Source. Other MapForge like games are Eigengrau's Generator (Free, Open Source), Campaign Cartographer (Paid), LDtk (Free, Open Source) and Dungeon Scrawl (Free).
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.
Eigengrau's Essential Establishment Generator is a tabletop procedural generation tool for towns, NPCs and much more. It creates paragraphs of text suitable to be read directly to players during a game.
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?
donjon.bin.sh is a freely accessible, online collection of random generators and other tools for pen-and-paper role-playing games. The collection provides a comprehensive range of advanced generators for creating names, demographics, maps, adventures and even entire worlds.
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.