There are several websites that sell unroasted or green beans in a range of quantities and will ship. I have heard that Costco or maybe it was Sam's Club were selling them as well (albeit in larger quantities). Keep in mind that shipping can be prohibitively expensive for small quantities. I order 12 pounds at a time from Sweet Marias and they ship in a flat rate USPS box; so shipping is very reasonable and only adds roughly a dollar per pound (for a twelve pound order).
I know are other good websites out there, but Sweet Marias has provided me with excellent customer service when I've had order issues (burst bags in shipping) and their website is very thorough, including forums, education and product reviews/recommendations.