I've always been a big fan of RTC. There's something unique about having a hard copy of the transcript to look over as soon as you're done practicing a take. I really like to go back and review /write from hardcopy and then listen to the same take over at different speeds. There's also a good variety of dense, fast material.
My only complaint is some of the best material for students is only available through Bryan College. I started out there, and the sound-a-like material and StenEd chapters were great practice.