I highly recommend Pathfinder(http://en.wikipedia.org/wiki/Pathfinder_Roleplaying_Game), it's basically 3.5 with further polishing, 3.5 was released under the open game license and pathfinder has continued it's tradition. It's also got a great support website: http://www.d20pfsrd.com/ and it's really fun. I'm running a Pathfinder game on a weekly basis after about a 5 year break and I'm really enjoying it.