I have to agree with Mirandalola about Khan videos. I abandoned them early because that time could be spent so much more productively. I found they were too general to help with what the MCAT questions were asking me and often too superficial to help me with passages. They are the bomb for P/S, but the 300 page document is more efficient. The best free resources I found were the P/S document (thank you MCATkings) and the SDN Q&A forum.
I'm also of the mindset that I want the best materials for preparing, free or not. If the best thing for P/S is free, then awesome. If the best thing for physics costs me $70, I'm going to pay. I'm applying right now and it costs so much $$$ that the $1000 I spent on MCAT materials is nothing.