QuicklyCode.com is a web gallery of cheat sheets related to programming. It’s got rating features bolted on which, with any luck, will help you find the best cheat sheet when there are several available for a given language or technology.
I haven’t owned a printer in something like 8 years, and that makes getting the most of QuicklyCode difficult for me. I may start making routine trips to FedEx Kinkos though, because I do love a good printed sheet of quick documentation.