I take a lot of my used books to half price, or to "stuff" which is a consignment store chain around here. It usually averages out to about $0.50 per book, but considering I pay less than $2 for most of them, and get quite a few for under a buck it's not a bad return on investment.
I'd be interested in any books you might have by John Lange as well as certain ones by Michael Crichton, Jeffery Hudson, & Michael Douglas. Condition & such aren't a huge deal to me since I'm aiming to get a complete set here.
You can also sell them on Amazon, too. I've sold a few things on there already.