The Character For Every Game Blog offers some really neat dungeon geomorph tiles, as well as a few nice complete dungeons. Plenty here to look at.
RPG Fantasy
Open Adventure Old School Adventure Game
Open Adventure is a free, open-source old school role playing game. From the description:
Open Adventure is a full-featured tabletop adventure game that offers out-of-box support for medieval fantasy and science-fiction expeditions. In Open Adventure, you play as a heroic or villainous figure free to explore the perilous world created by the all-mighty Game Master. Along your adventure you’ll battle ferocious enemies, solve complex puzzles, navigate labyrinthine mazes–and much more!
Morgalad Fantasy RPG Starterbook
Morgalad is a fantasy RPG set in a pre-medieval world. You can download the starter set for free.
GURPS Treasure Generator
For GURPS players, here is an online automated treasure generator.
Mythosa Fantasy Role Playing World
Mythosa is a free fantasy role playing world for any RPG system. It’s a very complete work, and cold be used right out of the box.