Wow cool, thanks for the replies.
I think one of my biggest problems right now is my compulsive need to collect discographies. It explains why my collection has grown so much in the last year. I used to keep my collection down to 30gb so I could fit the whole thing on my iPod, but when I realized that was silly, I sort of lost control of the whole thing.
Someone mentioned ambient. I went on a big ambient kick a few months ago, and have quite a lot of it. But I'm not often in the mood to listen to it, so I don't know it very well.
I suppose the best thing to do will be to leave it alone and just spend more time listening. Maybe I need a new rule says I have to listen to and rate five albums for every one I download!
Of course, I'm moving in 6 weeks and will be losing my amazing-ultra-fast-astonishingly-cheap internet connection, so another part of me is saying I should grab a few hundred more gigs before I go, just to be on the safe side