Cambridge's site is a little uncooperative, but this is a very cool project.
Shared by Brandon Keim – Isaac Newton’s Personal Notebooks Go Digital:
The largest collection of Isaac Newton's papers has gone digital, committing to open-access posterity the works of one of history's greatest scientist.
Among the works shared online by the Cambridge Digital Library are Newton's own annotated copy of Principia Mathematica and the 'Waste Book,' the notebook in which a young Newton worked out the principles of calculus.
Other of his myriad accomplishments include the laws of gravity and motion, a theory of light -- pictured above are notes on optics -- and his construction of the first reflecting telescope.