So, what can you do with the volumes you amassed?
The easiest answer is to donate them. If they're current, libraries would be happy to take the books of your hands. Thrift stores will usually take any book no matter their publication date, and anything they can't use will be donated to another charity or recycled. Other locally-based options include posting your inventory to sites like Facebook, Freecycle, or Craigslist. If you're thinking internationally, Books for Africa takes in-kind and financial donations to support local initiatives throughout the continent. Read more about their individual projects here.
If you're interested in earning back a bit of what you shelled out for that overpriced stack of paper, try your campus' buyback program, or check out online marketplaces like eBay's half.com or Amazon. I've used both websites and made some decent money, and the advantage is that you can set your own price. However, you are responsible for standard shipping, regardless of how much it costs to send each individual order. You are also at the mercy of the customer, who will be expecting their book to be shipped within 2 to 5 business days regardless of your own schedule.
Looking for instant gratification? I just discovered the wonders of Cash4Books.net, a locally-owned business out of Beaverton, Oregon. They have an A+ rating from the Better Business Bureau, and are committed to green business practices. Just type in the ISBN number(s), and Cash4Books will tell you if they'll buy it - and for how much. Shipping is free, and you get paid (via check or PayPal) when they receive the books. Since Cash4Books typically only buy books that were published within the last four years, most of the titles I entered were rejected. However, they offered me about $15 total for four books that were otherwise languishing on my shelf, and would only have been worth pennies on another online marketplace. For a half-an-hour of work, that's a good deal.
Do you have any other tips for finding new homes for your old textbooks?
Shared over at Frugal Days, Sustainable Ways