For DVD sets, Hannah Branigan's Obedience FUNdamentals (competition obedience) and Julie Flanery's TAP series (freestyle/heelwork to music). Both very clear, helpful, engaging, and thoughtful about common errors -- the really big ones like overshadowing cues and the small but equally common ones like always rewarding out of the same hand (which over time will often pull a dog out of position with anticipation).
I watch a fair number of sport-related DVDs, but those are my two favorites for covering the fundamentals of good, clear training mechanics and then taking them into more advanced work. I like Michael Ellis too, but I think I'm less impressed with those on balance just because I came to them later, when most of the concepts were already familiar, so it was more review material than new stuff by the time I got to those. If I had come to them earlier, they probably would have had a bigger impact.
For canine communications and learning to read body language, Sarah Kalnajs's The Language of Dogs was a game-changer for me. Not strictly "training," I guess, but certainly extremely helpful in seeing whether the message I intended to send was the one being received.
For youtubes, I like kikopup and a couple of other people. I haven't kept up on what's new in youtube tutorials for a while, though.
ARCHMX TDCH Pongu the Insane, CD-C, RE, RL1X6, RL2X5, RL3X2 (GSD mix, b. Apr 2010)
Crookytail the Tigerwuff, RL1, ITD (Akita mix, b. Jan 2011)