I'm going to go ahead and bookmark the crap out of this.

From the British Library's Digital Scholarship blog:

We have released over a million images onto Flickr Commons for anyone to use, remix and repurpose. These images were taken from the pages of 17th, 18th and 19th century books digitised by Microsoft who then generously gifted the scanned images to us, allowing us to release them back into the Public Domain.