Amulet Map Editor - The Amulet Map Editor is a new and innovative Minecraft map editor made by the Amulet Team, a team formed by the contributors that brought you MCEdit-Unified
WorldEdit - Minecraft MOD - WorldEdit is an easy-to-use in-game Minecraft map editor. Through a combination of commands and "brushes," you can sculpt your world or simply perform numerous terraforming tasks.
WorldGuard - Minecraft Plugin - WorldGuard is a powerful plugin with a large bag of tricks for server owners, server map makers, regular survival servers, and everyone in between!
MCEdit - MCEdit is an open source world editor for the popular game Minecraft.
Wurst - Minecraft open source hack
Universal Minecraft Editor - Universal Minecraft Editor is a software that allows you to modify the files of a minecraft world (NBT, items, mobs ...)