I think that this is absolutely brilliant. I have only ever seen drawings by Leonardo da Vinci here and there, maybe a book cover in recent years, or on a DVD case, a textbook cover and such. I have never seen a whole collection of his drawings in one place.
I am not sure if this is a definitive collection. It seems rather small if it is. But then again considering my exposure it could well be! But it is a very nice collection of drawings. You can click on images for a larger version. Or if you are so inclined you can download the whole lot as a .zip or .tar file. Not sure about copyright there so be cautious as to how you use them. The site also looks to be regularly updated with an update as recent as the 25th of February 2007.
I know that there a few here that I have never seen. I have an keen interest in the medical drawings, they are super, and very accurate considering the period they were drawn. Leonardo was a true genius and this is a window into that mind. A very nice diversion indeed.
Has anyone thought of making a website devoted to the works of our greatest historical geniuses? I can see a possible niche there for a social network or site of devotees, something. Whatever it was could be as cool as.