Lifehacker reader John is a finance student who found something very helpful in Wikipedia's new beta design. Any article can be downloaded or printed as a PDF, and multiple articles can be combined into a PDF book.
It may not be an entirely new-new feature for those who have long logged in and enabled beta features in their Wikipedia accounts, but it's a fairly recent addition for anyone who logs in at the mass-edited encyclopedia. In the left-hand sidebar, under "Toolbox," you'll find a "PDF version" link that uses Wikipedia's servers to generate a highly printable PDF of any Wikipedia article, no third-party tools needed.
More clever and interesting, however, are the "Create a Book" tools, which lets you add pages in real time as you dig through Wikipedia's knowledge tunnels. Click "Show Book," and you can re-order your pages, give your book a title and subtitle, and save it to your account for online reference or download a PDF for printing. As John points out, it's a boon to students who, while not relying on Wikipedia for their main study material, like to have a little reference guide handy for, in his case, "CAPM, APT, etc."