You've probably seen these, but maybe didn't notice them: Little Free Libraries. Find out more about these here. This is ours:
When you come by our construction site, you should -- things are going up, please stop in and visit our LFL. If you have any spare books lying around, bring them and add them. We're looking for children's books in particular, both in English and in Spanish. We noticed that there is quite a demand for them in our neighborhood, and it's a good way for us to contribute. The Fodor's guide to Paris? Take it! Not much of a demand for that one so far.