I don't have a top ten, but there are some coaches that leap out at me as being some of the top coaches to grace the NBA. In no particular order, because I don't want to argue over it, these are the guys that I think are very good, or elite if you will.
Popovich
Red Auerbach
Phil Jackaon
Pat Riley
Don Nelson
Rick Adelman
Jerry Sloan
George Karl
Rick Carlisle
I throw Carlisle in there because he's had a lot of change over on a yearly basis, and he still manages to find a way into the playoffs. Some of the coaches I listed haven't won a title, but if winning a title is what automatically makes you a great coach, then I'd have to throw Bill Russell in there, and I'm sorry, I don't think Russell was that good of a head coach. He just had great players in Boston. Whether you liked Don Nelsons style or not, he managed to win, and that's what it's all about.
Edit: Well when I don't look something up, I usually get it wrong, and I was wrong about Russell. He never won a championship as Boston's head coach. Came close, but didn't win. However, Tommy Heinson managed to win five championships back to back to back to back to back. Pretty impressive. So maybe I need to add him to my elite group.