I'm always mentioning the specialized databases often containing the full text of articles, reference books, etc. that libraries make available for free.
These tools (think of them as powerful vertical engines) can be accessed from your home or office, 24x7x365. If you're interested in learning more, I've written a guest column for BetaNews that provides and overview about some of what's out there. Yes, in the web age, the world of the library and the skills of the librarian extend well beyond the four walls of the traditional library building.