http://www.acsu.buffalo.edu/~kswiatek/StereoIntro.html
"An Introduction to 3-D (Stereoscopic) Photography",
by Kenneth Swiatek, a student of the School Of Information and Library
Studies at the SUNY University at Buffalo.
http://www.lib.unc.edu/ncc/pcoll/43stereo/
A collection of miscellaneous stereographs made in North Carolina from
circa 1870 to circa 1904. The policy page state that you must execute
a usage agreement with UNC. I don't know if this requirement is binding
on public domain images, so use these at your own risk.
http://www.hazyhills.com/mars3d/
A collection of stereo images from NASA/JPL, from the Mars rovers.
Interesting presentation where each pair is displayed as 3 images so one
can choose to view cross-eyed or parallel by looking at the left 2 or the
right 2 images. Anaglyphs are also presented.