Wow as a person who has played with and marveled at stereo pairs and just spending hours sitting with a viewer and a stack of cards sliding them closer and further out, this new project by the NYPL is just amazing. I had always wished someone would do this, now its a reality!
The New York Public Library has scanned and digitized their stereographs and allows users to make animated gifs, and 3d anaglyphs with their simple and straight forward in browser tool.
This is quite a rare opportunity to see some amazing photographs from their collections, and a bit easier with an animated gif to see them work, as using the hand held sterogram viewer device you need to get it just right for your eyes to "see" it. You can view the images created by others, or you can try to improve their's, or start making your own.
Popular gallery (great examples):
Many were taken from "United States in Stereo: In the Robert N. Dennis Collection of Stereoscopic Views" 40,000+ Steroscopic views.
I hope you werent working on anything important, and this might take over your next few hours