Better World Books is an online bookstore that offers free worldwide shipping. They offer new titles as well as used books and textbooks. They are affiliated with over 2300 college campuses and 3000 libraries. So far, they sold over 117 million books for $15 million, and put that into funding for literacy and education.
Daedalus Books is an online bookstore that offers the residual, unsold new books, but you might want to give them a second chance. Their prices are really cheap, and you can get a discount of 10% if you sign up for their email list.
They are shipping worldwide, and the cost depends on the weight of the shipment. It might take 3-6 weeks for the shipment to arrive.
Booktopia is an online bookstore based in Australia, that offers:
Free shipping isn't available to everyone. Booktopia sends you an email when that option is available. During that time, you can pass the code to a third party (friend, family member, colleague, etc.). This is done because their shipping price is fixed, no matter how many things you order in one go. It's always $6.95.
This store offers their services only in Australia (including the rural areas) and New Zealand.