This will be updated as I come across them, or if people bring them to my attention:
Written material
Pilot's Handbook of Aeronautical Knowledge (FAA)
Hal Stoen's page - scroll down to the Tutorials web site. Old-school web site with fantastic content.
AOPA's NEW PILOT'S GUIDE TO ATC COMMUNICATION
Videos
Air Boyd Aviation Safety and Training playlist
Jason Schappert's youtube channel - lots of high quality instructional videos from m0a.com
VFR Charts (youtube playlist)