My list is similar to Ian's.
Ray Hunt and the Dorrance brothers
Ken McNabb (My best friends have ridden with him quite a bit, and he has a year long internship program that I am considering in the future)
I'm nota big Clinton Anderson fan. I think he knows his stuff, and is good at helping people with their horses. I think he can be a little bit too heavy handed and doesn't always time his releases properly. He's also gotten very gimmicky, and his sportsmanship with other trainers could use some work.
"But I can tell you this: When you get to square ten, all of square one will be in it." RayHunt