They are organized in only the loosest of terms, kinda grooped by size or subject, and even that never really lasts that long. Still, I almost never have trouble finding something I want.
I can get very Farienheit 451 about books, perhaps because I used to move so often. I borrow from friends and take out from the library as often as possible and then I periodically purge and give away to charity. I just don't understand some people's emotional attachment to books, where they have practically every wall lined with dusty shelves. How is it different from those strange old ladies collecting stray cats?
Tapes and CDs kinda purge themselves, as they're all rubbish and it's not long before the tape weares out from overuse or the cd scrathes beyond listening enjoyment.
Other than that, I try to set resonable limits. For example: skating tapes. I won't keep anything other than nats, worlds and Oly, and even then I try to limit it to one tape per event. It's been about a decade now, so don't be surprised if you see the whole collection at a yard sale one day.
My dream house would have all cubboards, so it would never look cluttered, but until then I keep the books mostly on shelves and the cd and tapes in drawers. Exposed is so messy looking and at least books are kinda nice looking, tapes and cd are just plain ugly.