Rules-Lite RPG Systems
FURTHER - The Freeform Universal Risus Tabletop Have Everything Roleplaying system.
Questweaver - A D20 inspired rules-lite RPG system.
D&D Campaign Setting: Calbion
This started out as just a background world for a D&D campaign I got involved in.
Latest Edition:
Calbion World Guide 2nd Edition V.1.6
Older Editions:
Calbion World Guide 2nd Edition V.1.5
Calbion World Guide 2nd Edition V.1.4
Calbion World Guide 2nd Edition V.1.3