TEdit - Terraria Map Editor - TEdit is a stand alone, open source map editor for Terraria. It lets you edit maps just like (almost) paint! It also lets you change world settings (time, bosses downed etc), edit chests and change sign, make epic dungeons, castles, cities, and add rewards for your adventurers!
TerraMap Web is an interactive Terraria v1.4 world map viewer that loads quickly and lets you pan, zoom, find blocks, ores, items in chests, dungeons, NPCs, etc.