Rob Conely of A Bat In The Attic blog has written a document on making a Fantasy Sandbox.
RPG
Medieval Demographics For Fantasy Worlds
Creating a fantasy world? Running a medieval fantasy RPG? Here’s a great article on Medieval Demographics, based on the Paris tax lists of 1292 and other original sources.
Gothic Fantasy Adventure Generator
Tales of the Grotesque and Dungeonesque offers a Gothic Fantasy Adventure Generator, which produces sentences for adventure seeds.
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.