What do you do with books after you read them?

[Warik]

I have a buncha books I've either already read, haven't read but won't read, or have already read and will never read again sitting around and taking up space. Do you people resell them on Amazon.com or something after you've read them or do you load up shelves and shelves with 'em?

I've got my copy of Atlas Shrugged here which cost me $40 and I'll never read again, but I can't seem to get myself to sell it. lol