Audio aids are great! There are several good ones - find the audio that goes with your casebook or look for ratings/user comments on amazon. Often the audios follow a casebook - that really helps you have an intelligent discussion in class and helps with material comprehension. I would not lock on to any one particular "brand." I used Gilbert, Sum and Substance, and Law School Legends and they were all good - get an early start and find them cheap used on Amazon or Ebay. They are very helpful supplamenting the material that the profs cover. I had some great Civ Pro disks that really cut through the fog of the FRCP and were downright entertaining b/c the audio professor did such a great job using memorable examples. I still remember his example of pleading special damages referencing a case where a guy got hit by a car, suffered routine injury, and nerve damage that caused him to have a permanent erection - the "special damages." You expect broken bones in an accident, not a permanent erection. He said his wife would be pushing him in front of cars. Cannot recall who they were through though.
I just picked up some Law School Legends audio cassettes on evidence and property for a small amount. Is Sum and Substance superior to the others? It seems they are more expensive- but a few people have been happy with them.