Green Reads has launched a crowd funding campaign on IndieGogo to build 15 eco-friendly, used book vending machines. Invented by Dana Clarke, the machines require no electricity and they'll allow libraries, charities, and book retailers a way to sell used books and create a sustainable source of revenue. Green Reads is looking to raise $75,000 ($5000 per machine) by May 19. Once operational, the machines will be donated (not sold) to libraries and charities. You can get a lot more information and contribute to this worthy campaign right here.