I went to a wonderful little museum yesterday, not too very far from NYU's digs.
All of the stuff in the British Library's exhibitions used to be at the British Museum, but the collection of documents and manuscripts grew large enough to warrant it's own space in the Library's rather ugly modern building at King's Cross. But the space is small enough that you could make a respectable visit in under an hour -- though you need a little more time to really appreciate it.
Among the highlights are not one, but two original drafts of the Magna Carta (only four survive), as well as the Articles of the Barons that preceded it in 1215. There's Handel's draft of the Messiah and drafts by Mozart, Bach, and Beethoven (Beethoven wrote notes in big, crazy, Van Gogh-esque strokes. I think those two would have gotten along fine, if they didn't kill each other first). Original handwritten manuscripts from Jane Austen, Charlotte Bronte, Shakespeare, and James Joyce -- another kook with deranged handwriting. They also have a lovely collection of illuminated manuscripts and ancient religious texts in Hebrew, Sanskrit, and Arabic. Since you obviously can't leaf through this stuff, you can go to a back room and virtually turn the pages of the Lindisfarne Gospels and Leonardo Da Vinci's notebook on computer.
There was also a nice display of Beatles' lyrics scribbled on napkins, notepads and children's greeting cards where you could see songs like In My Life and Hard Day's Night taking shape. That's one drawback of the information age. I bet musicains don't scribble lyrics on airline cocktail napkins as much anymore. They jot them in their Palm, or some damn thing. Not nearly as romantic, if you ask me.
If you're in London, definitely check this place out. It won't take long, it's not crowded, and, like most museums in London not owned in part by the Windsors, it's free.