Hey
I was just about to purchase a programming book from Amazon when it struck me, why aren't you using Amazon's affiliate program to earn the site some extra residual income. Simply posting links to recommended books and including your affiliate ID is easy as it sounds. Although I'm not too familiar programme since I only deal with PPC atm (I'm a Internet marketer), therefore this might vary. You might already be doing this via CS, but I doubt it.
But seriously, It's a nice method for members of the site to give a little back, and it requires absolutely no effort on our part. You could even set up a little more, and create a bookstore using ready made tools if you wanted to scale it up.
Anyway if you want any more information, feel free to ask away.