We get most of our new books through this charity which receives the books from publishers and distributes them to organizations that serve children in low income areas. There are two places to purchase books on the website. In order to purchase from the Book Bank, where the books are free, but the shipping is generally under a dollar per book, you need to attest that you are serving children living in poverty. However, anyone can buy kids' books at the First Book Marketplace, where they sell books to cover their operational expenses at around 50% off of the cover price. There are also lots of free resources for teachers here. 

This organization mails books to children age 4 and under for free. They work with donor organizations who operate in cities around the world. You can check to see if your zip code is one that has been adopted by an organization and is eligible for free books. 

This is a Florida literacy program that mails books to kids enrolled in a Florida school in grades K-5 who are reading below grade level. We have been advised that if the parents' housing is unstable, the books can be delivered to the school to be given to the child there. Children can indicate their interests and get books  that they choose. 

This organization promotes reading by providing resources to set up mini-libraries through stewards who install and maintain the libraries. Check out the map for these libraries around the world - including ours!