Wayne Houchin's live lecture was awesome - he taught some tricks but his philosophy behind how he creates was inspiring.
Shoot Ogawa's work is, quite possibly, more beautiful from "behind the scenes", and he's very inspiring.
I think Kozmo's live lecture was one of the first I ever saw and that man knows busking inside and out.
Shawn Farquhar's has stuck with me a long time. That man is one of the genuinely nicest people I've ever met, and his love of magic shines through everything he does. Also, I was his volunteer for his version of Omni Deck and I didn't see a thing.
For online lectures - I only have some from Penguin. Peter Turner's got some good advice for mentalists, but you have to kind of read between the lines sometimes - He's a natural at his style, and because of that he can't always communicate the intricacies. Derren Brown's gives you insight to his path, but there's no tricks (which I don't mind). Rob Zabrecky's is delightfully odd and full of theatrical advice.