I'm pretty fond of B's autograph manuscripts. It's as if his sketches are plans for individual tactics, and the manuscript is the enactment of the entire battle - sometimes things need to be changed on the spot, hence the X's and cross-outs to be found all over his manuscripts.
The BeethovenHaus in Bonn has a great website with loads of archival material including manuscripts, sketches and letters. Here is a short animated autograph score to the beginning of the 6th (Pastoral) Symphony.
Juilliard also has a great manuscript collection.