The Nine Worlds is a classic Hex-crawl/Dungeon-crawl campaign in the West Marches style, using HackMaster 4th edition as the system.
(The Nine Worlds) wiki includes a general description of the setting, its mythos (which is loosely based on Norse Mythology), and the rules changes from HackMaster. Quite a bit of additional material is currently not up on the wiki in the interests of preserving some mysteries for new players, but players are encouraged to add their own accounts, maps, and material to the wiki as they explore.
*The West Marches
*The Nine Worlds Wiki