What about donating to Goodwill, Salvation Army, or some other charity? If you have classics/appropriate fiction, your local public high school will, I'm sure, love to get these. Here in AZ, we have an organization called, "Volunteer NonProfit Service Association" which collects books and resells them at a huge book sale every February. All the proceeds go to charity. Or, for romance novels,
http://www.share-the-love.org/
What about your local crisis shelter, or homeless shelter? I'm sure there are many good quality organizations that would appreciate a donation of our old books.