Neebo a new online textbook rental website is allowing the first 100,000 customers a free textbook rental. The fine print says you just be a fan of Neebo on Facebook. Shipping is not free but its a lot cheaper than renting your textbook from another site.
Ground (3-7 business days): $7.99
2nd day (1-2 business days): $13.75
Next day (1 business day): $20.75
They have a pretty good selection and you can't beat the price.