Flickr: The Commons
Here's a fantastic collaboration with the Library of Congress. We are being asked to collectively tag historic pictures with no known copyright restrictions. Wonderful idea! Are you watching, British Library?
Flickr: Photos from Powerhouse Museum Collection
The Powerhouse Museum in Sydney—who have been doing some great stuff with public tagging already—have joined the Library of Congress in putting their photographic collection online for crowdsourced tagging.
Related links
Flickr: National Maritime Museum's Photostream
Flickr Commons just keeps growing and growing. Now there are wonderful collections of pictures from Greenwich available for us all to peruse and tag.