For some people, books are like trophies -- a statement of achievement and a reflection of one's intellect, education, travels, and interests. A true bibliophile may find it emotionally difficult to get rid of books. If it's time to weed shelves, consider these options.
Give books away. Give a book you have already read to a friend who you know would love it. Or donate books to your local library, community center, or charitable organization.
Swap. BookMooch and PaperBack Swap are examples of online communities for exchanging used books. Users give away books for credits and then use credits to obtain other books. (Not the best for reducing clutter, but it's a good way to get books for free.)
Sell. For those who need a financial incentive to de-clutter, Amazon makes selling used books easy. Once you've set up an account, listed your books, and made a sale, Amazon will e-mail you a packaging slip and shipping label. They add shipping costs automatically to the selling price and send you an electronic deposit periodically. Half.com (part of eBay) is another online venue. While old college texts and last year's bestsellers might not fetch a lot, a market always exists for such titles as big, graphic coffee table books.
Flickr photo by cogdogblog
For more cleaning tips, check out What's A Disorganized Person To Do?