Staples is crazy evil, and I wouldn't buy a pencil from them after what they did to a member of my family, let alone make a "donation" that they will make money off of.
A really easy way to get rid of that sort of stuff is to post it on Craigslist, which is also free, AND you don't have to take it anywhere (unless you agree to deliver or something)

The Harvard Bookstore is awesome.