Now go outside and look at the sky.
LIFE Photo Archive
Just stumbled over this one: Google now hosts scans of more than a million LIFE photos from the 1800s up to today.
From a first glance, there are endless opportunities for research and just idle Googleing. Hundreds of images from the Yangtze in the 1940s, the San Francisco Conference, historic shots of the National Parks, American Diners... there's lots of good stuff in here that has quite possibly never been published in the magazine.
It's great to live in a time where more and more of these once unaccessible archives are opened up, never to be more than a few mouseclicks away.