0One Dungeons
Anytime anyone asks me about maps for a fantasy game I point them to 0One Games. They are not the most graphically intensive maps, most being b&w or blueprint, but they are always reasonably detailed and very reasonably priced at $1-3 per map. Over the last several years I've managed to buy up almost all of their individual maps, leaving me with just a few of the box sets I need to get. This BOH is a great buy if you don't have any of the Dungeon Under the Mountain series (which I hadn't, until now).