I stumbled upon this site today and thought I'd share. It has a ton of great old images. I especially like the WWII-era photos in color. Anyway, I know there are some here that can appreciate them so here's the site.
Shorpy | The 100-Year-Old Photo Blog (http://www.shorpy.com/)

A few samples (higer-res versions available on the site):

http://www.shorpy.com/files/images/1a34797u.preview.jpg

Washington Monument
http://www.shorpy.com/files/images/03248u_0.preview.jpg

The hanging of the Lincoln assasination conspirators:
http://www.shorpy.com/files/images/00836u.preview.jpg

US Capital Dome - 1863
http://www.shorpy.com/files/images/03247u.preview.jpg