Some folks in London have started a campaign to provide free second-hand books to commuters on London’s tubes.  Here’s their schtick:

The London Book Project is a free book exchange on a massive scale.
Using the London Underground as a high speed distribution network, we
aim to bring real literature to London’s commuters. Scrap the
freesheets – read a free book instead!

Over the next two weeks we’ll be distributing thousands of second
hand books across the tube and we want YOU to get involved. If you see
one of our books, please pick it up! Then read it and replace with any
book of your choice. Let’s make the tube a giant, free library!

Found via Boing Boing.