NASA definitely has a great program for beginners. They have excellent instructors (both in car and classroom). Most of the other groups mentioned are great too. For a first timer, running with a group that's just holding an HPDE is better IMO. You usually get more track time, and it's a more relaxed atmosphere. Everyone is there just for fun. No races/racers (nothing against racing/racers. I'll be one sooner or later. It's just a little more...ummm...intense, and not to mention crowded). On the other hand, if you want to try to catch some racing between sessions and classroom, NASA is a great time.