I used Audiolearn and found them to be very helpful. I’ll never forget sitting at a stoplight listening to this booming deep voice say “momentum is ALWAYS conserved.” Believe it or not, there was a problem about that on the MCAT. I answered it in 2 seconds flat and moved on. 🙂 Also, I know this is not a good idea…but I used the flashcards (I forget who makes them…I bought them at Amazon) when I was in the car. I’d read one side and then say out loud everything I knew about it. Dangerous, I know…but it helped pass those hours in the car and helped with my studying. Good luck.