have some old school bookmarks with your URL on it printed.

Sneak (thats the sneaky part) into your local library and slip those bookmarks into the books

Disadvantage: If you get caught they make you mob the floor
so it might be actually a good idea to approach them officially and strike a deal

This could work if your target market matches in some way the library clientele e.g. students, school kids
(all those poor folks who dont own an ebook reader or IPAD LOL)