Project Gutenberg makes non-copyrighted texts available on the internet. They use a team of distributed volunteer proofreaders. Today they announced that the distributed proofreader project has just completed its 25,000th book, and I think it is fun that it happens to be The Art and Practice of Silver Printing by Capt. Abney and H. P. Robinson.

The book:
Distributed proofreaders:
Project Gutenberg:

I wasn't completely sure what forum for this, but since the book has a picture of a contact printing frame on the cover, I thought here might be appropriate.