Another vote for 10MS pilates videos, especially with Lara Hudson!
I like the original and the ball ones the best, though I have all of hers.
I have the Hillary Burnette Intermediate, I seriously need 2 try that!
One which may not have been mentioned yet, which I'd recommend, is the Project You Pilates Core, it is surprisingly challenging.
I impulse bought the Mari Winsor Slimming Pilates set (with the band apparatus) and it's well designed but boring. It's my first experience with Mari.
I don't usually do them (preferring 10MS), but Ana Caban has some very good challenging routines. Her Pilates for Abs is tough!