The boston.com website has some really great photo collections in their 'The Big Picture' section. There was a group of images from Russia in the early 1900's taken by Sergei Mikhailovich Prokudin-Gorskii . The pictures have some pretty amazing colors in them. When I was doing some initial research on the subject, I came across the Autochrome Lumière process that seems exceptionally interesting. Using potato starch and different size particles they were able to create color photos on a single pane of glass (which was used for negatives at the time). At first, I assumed this was how Gorskii was creating his color images, but it turns out that Gorskii was a bit of an inventor himself, and had come up with his own three-photo process for taking color pictures.
The Library of Congress has a decent sized collection of Gorskii's images. The collection seems to be a bit random in it's numbering - it seems there are several specific groupings of images, but they're sort of mixed together. Overall, though, I find the collection very fascinating. The Library of Congress' website is really annoying to use for basic photo browsing, so I wrote my own interface for it available here .
Some of the images are pretty stunning. Some of the images, I wonder if anyone will ever know who is in them or any more specifics than what you can see. I imagine there are notes somewhere, but, possibly not.