About Projectors and Slides
http://inventors.about.com/od/mstartinventions/a/magic_lantern.htm -- A brief (but technical) overview of the lantern slides

http://www.mccord-museum.qc.ca/en/keys/virtualexhibits/magiclantern/ -- An excellent online exhibit with McGill's collection of slides

Online collections

http://www.life.uiuc.edu/edtech/entomology_slides/index.htm -- a site on Entomology related slides

http://geoimages.berkeley.edu/GeoImages/LanternSlides/LanternSlides_TOC.html -- Berkeley's Geography Collection

http://www.brynmawr.edu/Admins/DMVRC/lanterns/ -- Bryn Mawr's Classical Antiquity Collection

http://www.vrc.iastate.edu/lantern-collection.htm -- Iowa State's Landscape Architecture Collection