I have to say that I'm a huge fan of the British Library.
Why you say?
Check out their Turning the Pages section.
You can digitally "turn the pages" of a few original works and books.
For instance, do you want to look at Jane Austin's The History of England, written in her own handwriting and even illustrated with cute pictures of kings and queens?
Or maybe the original Alice's Adventures in Wonderland written and illustrated by Lewis Carroll himself?
Or maybe Mozart's musical diary, or Leonardo da Vinci's sketches?
Most have audio commentary that you can turn on or off, you can zoom in or out, and other fun features.
My favorite....the Lindisfarne Gospels:
Check it out!