Everyone likes getting something for free. Aside from herpes, I expect. Anyway, there are millions of articles, adventures, add-ons and RPGs out there available in full or sample form for free or very little, so let's gather a few recommendations - with links! - and share them here. Please add your views on whatever you're linking to, if appropriate, so that this doesn't become simply a big list of anonymous things to click. A couple of starters:
That link goes to a forum post on the Original D&D Discussion forum where you'll find links to the individual booklets, or an online hyperlinked version, of the Delving Deeper rules. Free of charge, but there's also a very cheap combined volume on Lulu, linked at the same place. DD is a Dungeons & Dragons retroclone based on only the very earliest publications, specifically Chainmail, Dungeons & Dragons and some material from The Strategic Review (you can read an excellent post here describing exactly what it is and how it compares to some other retroclones). It's been very rigourously compiled and edited, a really top-notch job, and represents one of the very best ways to try early style D&D without either spending a fortune or battling with the ambiguities of the original booklets.
Hex Games have a very extensive catalogue of published material for the second edition of their generic QAGS system, including a free set of "Qik-Start Rules" (sic). Most of the books and PDFs are available for pretty reasonable prices and there's a ton of variety (Really, a ton: WWI flying aces who just happen to be gorillas, chimps, orangutans? Try Aces & Apes! A supplement based on Gilgamesh? Yup, they do that too), but of particular interest to this cheapskate thread is the selection of 1st Edition PDFs. Included is the original edition of the core rules, as well as a horror scenario, setting book, a couple of monster books and an equipment book called Stuff which I'm afraid is the only one I'd suggest not bothering with. I've been meaning to run the horror scenario, Terror at Camp Waka'Naka, for a while and might take it along to the UK Games Expo in a few weeks. At the bottom of the page is M-Force: they're still working on a new version, but this is a complete, free and enormous RPG of monster-hunting. Unlike the small pamphlets of the other first edition stuff, M-Force was a big perfect bound paperback running to several hundred pages. All of these 1st edition freebies have slight problems, primarily down to being fairly basic in terms of layout and presentation, but the material is solid (excellent, in some cases) and you can't beat the price. I'm impressed that Hex has put this stuff online instead of burying it the way many companies would.
Go on then, show me your linkies