A comprehensive online Med school may still be some way off.
The evolving list below contain some great resources but medicine is still a bit under-represented (you-tube excepted)
Khan academy 2600 (and counting) short videos covering maths, science and everything – currently about 30 medical presentations
CNX.org Massive open courseware site but with limited medical resources
iTU some good stuff but not loads – locked into the Apple walled-garden