Little Free Libraries are crate-sized DIY lending libraries that one can build (or purchase) and install in a place to be accessed by the public. Your Little Free Library is stocked with books that you don’t actively use anymore, so that others can read and benefit from them. Users can check-out on their own, and either return the book borrowed, or replace it with a book that they’re ready to share.
Here is a news segment about how they started:
via Library Stuff