If you have a library card chances are your city/county library has a subscription to Safari Tech Books Online. Mine does anyway. Our county carries some 250 titles. Also, If you can build a relationship with the right person at your library, chances are they can add books that they aren't currently subscribed to. Those making the selection decisions are usually not techies and *may* apprecite your feedback on their collection.
in reply to Free Perl Books
Also, it's a good chance that your library subscribes to other databases and services that carry tech books as well. Ours also allows me to access The Net Library.