Groove Holmes is the shiznit! He started out on organ... he didn't switch over from piano, so there's something about his playing that is different from everyone else. Number one, his basslines are so solid and swinging and he was an absolute monster on the pedals. Any of this recordings from the 60s are gems.
Check out some of Bill Heid's records, too. He's the best kept secret in jazz organ. I can't believe how much press Tony Monaco has gotten and Bill is still so obscure. Don't get me wrong, Tony is a great player, but Bill Heid is a fantasic player too and composes some really memorable songs.