If you happen to have some older edition Dungeons and Dragons books hanging around, you might be just the person Wizards of the Coast is looking for.

In partnership with DriveThruRPG, Wizards is offering $50 for each title you are able to scan and that is listed on this spreadsheet. There are close to 600 titles that Wizard needs to replace on their digital archive, whether lost to time, damage, or theft. The books they need are mainly from the original D&D and 2nd Edition though they do need a few from other sets as well, all the way up to 3rd.

All you need is a high-resolution scanner (most consumer models will do), some time, and the books themselves.

via Goodereader.com