E6

E6 is D&D 3.5 edition, but normal level progression stops at level 6. After that, a system of granted feats and basic leveling mechanics kicks in. It's meant to prevent the game from getting ridiculously overpowered and overmagical, while still allowing very lengthy character progression. The system is free and entirely summarized here:

http://forum.rpg.net/showthread.php?t=352719