I never throw out stuff at the end of that semester, but when the next semester ends, and I go to file the most recent stuff, I look through my old notes and books and whatnot and then decide what to sell/recycle. Its always nice to have that cold hard cash in your hand as a reward for getting through a ****ty class. I'm also a big fan of selling books on the internet cause our campus bookstore really rips us off, especially if you're prof decided you needed a new edition.
As a side note - I was keeping a bunch of old class stuff because I thought I would be needing it to review for the MCAT. How silly of me! With my review class (PR), I've got more than I could ever read and review, and its a heck of a lot more comprehensive than my random class notes. If this is your motivation for being an academic pack rat, you ought to reevaluate why you're keeping that many pounds and cubic feet of crap you'll never look at again.
Overall message: Keep it for a semester, then trash what you've haven't needed.