Do you have boxes of books waiting for a new home? Powell's stores will, of course, gladly take some of them, but if you're not in the mood to schlep heavy boxes only to find out that they're worth next to nothing, you might want to do some research first.
Instead of taking them into the store, find out which books Powell's will buy from the comfort of my couch! At the Powell's website, you can enter a book's ISBN number, find out what they'll give you, and then ship them, (Powell's will even pay for the shipping!). Sweet. Granted, you'll probably spend the money you get on more books, but at least you're clearing some space temporarily.
Before you gather all your dusty volumes together to sell, read a bit about Powell's online book buying policies.