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.

Links:
The book:
http://www.gutenberg.org/ebooks/42547
Distributed proofreaders:
http://www.pgdp.net/c/
Project Gutenberg:
http://www.gutenberg.org/

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.