I used this site a few times in college - http://www.notehall.com/ http://www.notehall.com/ . The downside is you have to pay for notes, study guides etc. but

I used this site a few times in college - http://www.notehall.com/ http://www.notehall.com/ . The downside is you have to pay for notes, study guides etc. but they let you preview the notes and then leave reviews after you've purchased.