Ship them to appropriate recipients. The donor has little work to do, but may have little or no say in designating a recipient. At the other end of the spectrum of donation projects, a donor may do it all. Select books according to recipient guidelines, pack them and ship them directly. Multinationals in particular may be on the lookout for good will projects.
Shipping is the hardest part of the project to arrange.
The method which is cheapest per book is shipping a container-load of books surface mail. Check van lines, shipping agents, and international firms for free or low-cost shipping on a space available basis. Contact the embassy or consulate of the recipient country in the U.S. - sometimes they can help with shipping. The U.S. embassy in the recipient country may have some suggestions. Certain U.S. academic grants may include provisions for shipping books, as may certain linkage grants between academic institutions in the U.S. and the recipient country.