TurboTax Federal Free Edition.
Libraries aren't just the mark of a civilized society -- assembling, curating and disseminating knowledge to all comers! -- they're also a cheapskate's best friend. Anyone who's interested in saving money probably already knows about the free Internet access, daily newspapers, DVD and audiobook borrowing, and book lending (duh). But local libraries go beyond that -- many host community meetings, book readings for kids, author signings, and workshops, as well as providing free or low-cost meeting spaces.
My favorite cheapskate pro-tip for libraries is asking reference librarians really hard, chewy questions. For example, any time I have a question about science fiction literature ("When did William Gibson first utter 'The future is here, it's just not evenly distributed'?" or "What was the time atomic weapons appeared in science fiction?") I ask the librarians at the Merril Collection, Toronto's incredible science fiction reference library, whose librarians are ninjas in such matters. But it's not just esoterica: many's the time I've walked into a good library and asked the reference librarians for help with something really chewy -- the sort of thing I might otherwise pay a researcher to find. Unlike a paid researcher, reference librarians usually don't just give you the answer, but rather take you by the hand and guide you through the use of library resources (including proprietary databases that aren't accessible over your home Internet connection), giving you an education in problem-solving as well as the solution to your problem.
Librarians, ultimately, are in the business of evaluating the authority of information sources, a problem that has never confronted more people than it does in the era of the Internet. I'm particularly looking forward to the day that hackspaces and libraries begin to realize that they're approaching the same problem from different directions, and a corner of the local branch into an e-waste recycling depot where librarians and tinkerers will help you build and outfit your own PC, giving you the technical and information literacy to understand what your computer is doing on your behalf.
(Image: Cutting Libraries in a Recession is like Cutting Hospitals in a Plague., a Creative Commons Attribution (2.0) image from daniel_solis's photostream)