Here's an internet miracle: Charles Darwin's complete papers, never physically assembled in any one place, many of them unpublished, are now available online - and for free.
Darwin was responsible for one of the greatest leaps of science of all times, when he formulated his theory of evolution. The collection currently contains more than 50,000 searchable text pages and 40,000 images of both publications and handwritten manuscripts, with much more still to be added. It even includes a missing notebook recording Darwin's five-year voyage to the Amazon, Patagonia and the Pacific aboard HMS Beagle. (Fortunately, the text was micro-filmed before it was stolen.)
More about the collection in the Guardian.