I don't want to hijack the thread, but those who have sold books, dvds etc, have you made quite a useful amount of money?
I have about 400 books which will go to charity shops soon as I'm moving into a smaller place so this might be an idea..
My fiance sold some coins and things he'd had for ages, and one of the things which made a really decent profit was a Californian police badge he bought for $15 about 5 years ago, and it sold for around £400 on ebay. Things you don't expect to be valuable are often priceless to someone else.
I used to buy things in bulk and then sell them in smaller parts. When Pandora first took off, I bought a large lot of replica beads (never advertised them as real, but people were looking for a cheaper alternative) for £5 and sold them one by one for £30 total. Then I spent that £30 buying more etc etc and made quite a lot.
I also bought other things because the beads would sell around £10 worth a day, so when I had a little more to invest they weren't selling fast enough, so I got things like the bracelet strands (again, replicas, got 10 for £10 and sold them for £2 each, and bought more when I was in profit).
It was quite a fun summer actually, but then eBay put their prices up so it wasn't really worth the effort anymore, because of the time it took to go to the post office (I don't drink and it's an hour round trip that I was having to make daily) and I had to stop when I got back to college because it was taking too much of my revision time.
Now I'm fully qualified in my career its not really worth it any more. But back at school I had a few things on the go...
In a popular game I found a loop hole where items could be multiplied and then gifted to other players on line. I basically sold my "time" not the item its self so completely legal and for 30 minutes each day after school I was making £20-£40.
Car boots. I stuck to electrical items because their ebay value is pretty easy to determine. I've brought things in the past and made up 10 fold on what I originally paid.
I've also had friends who have brought things from charity shops and sold for a decent profit.
There is so much easy money to be made through ebay in your spare time at college/uni. Beats stacking shelves part time as well.