Webvision: The Organization of the Retina and the Visual System (University of Utah).: Comprehensive site on medical vision research
http://webvision.med.utah.edu/
The Joy of Visual Perception. (Peter Kaiser): Online book on vision including colour vision; you can even ask the author questions (but read the book first!).
http://www.yorku.ca/eye/titlepg.htm
http://www.yorku.ca/eye/question.htm
Visual Perception (Daniel Chandler): Various topics on visual perception (not colour)
http://www.aber.ac.uk/media/Modules/MC10220/visindex.html
Levine, Michael. Colour Vision (overview)
http://flash.lakeheadu.ca/~mwesner/COLORreadings/ColorVision(Overview)/ (36 pdf pages)
The Physiology of the Senses. Transformations for Perception and Action (Tutis Vilis): Elaborate demonstrations of The Eye, The Visual Cortex, Visual Perception of Objects and Motion and other topics (not colour vision) available as flash demonstrations and PDFs
http://www.physpharm.fmd.uwo.ca/undergrad/sensesweb
Colour and Colour Vision: Background Information (Colour and Vision Research Laboratories).
http://www-cvrl.ucsd.edu/background.htm
The Bases of Colour Vision (Brian Wagner and Douglas Kline)
http://www.psych.ucalgary.ca/pace/va-lab/Brian/default.htm
A Chronological History of Vision Research (Jack Yellott)
http://web.archive.org/web/20040407004054/http://aris.ss.uci.edu/cogsci/vision/yellott_1600.html
http://web.archive.org/web/20040407004054/http://aris.ss.uci.edu/cogsci/vision/yellott_dates.html
Interactive online/downloadable programs
Vision Science Demonstrations and Publications (Hans Irtel).
http://www.uni-mannheim.de/fakul/psycho/irtel/research.html
PXLab Vision Demonstrations (Hans Irtel).
http://www.uni-mannheim.de/fakul/psycho/irtel/pxlab/demos/VisionDemonstrations.html (online)
Older downloadable Widows program (CVD.exe), with notes for experimenting with various colour vision phenomomena, still available at:
http://www.uni-mannheim.de/fakul/psycho/irtel/cvd.html
Site also includes a collection of historical colour diagrams
http://www.uni-mannheim.de/fakul/psycho/irtel/colsys
Project LITE - Atlas of Visual Phenomena: Dozens of demonstrations of optical illusions and visual phenomena. NOTE: The demonstrations of additive and subtractive mixing used in the course are from this site:
http://lite.bu.edu/ (Online or download - Windows/Mac)
http://lite.bu.edu/vision/applets/lite/lite/lite.html
http://lite.bu.edu/vision/applets/Color/Addition/AdditionMove.html
http://lite.bu.edu/vision/applets/Color/Subtraction/SubtractionMove.html
Spektral (Pehr Sallstrom): Programme for visualising the relation between colour and spectral energy distribution
http://home.swipnet.se/pehrs/english/ix.htm (home page)
http://home.swipnet.se/pehrs/english/visualspd.htm (Windows 98)
Sallstrom, Pehr. Using a Personal Computer as a Visual Colorimeter
http://home.swipnet.se/pehrs/english/Downloads/colorimetry.pdf
Sallstrom, Pehr. Teaching colorimetry using an ordinary PC
http://home.swipnet.se/pehrs/english/colorim.htm
Sallstrom, Pehr. A Computer Program for Visualising the Relation between Colour and Spectral Energy Distribution
http://home.swipnet.se/pehrs/english/Downloads/spektral.pdf
Optical Illusions
69 Optical Illusions & Visual Phenomena (Michael Bach): Try the "Lilac Chaser"
http://www.michaelbach.de/ot/
http://www.michaelbach.de/ot/col_lilacChaser/index.html
Optical Illusions (eChalk): Outstanding illustrations of influence of surround on colour perception.
http://www.echalk.co.uk/amusements/OpticalIllusions/colourPerception/colourPerception.html
Akiyoshi's Illusion Pages (Akiyoshi Kitaoka)
http://www.ritsumei.ac.jp/~akitaoka/index-e.html
Illusions and Demos (Edward Adelson):
http://web.mit.edu/persci/people/adelson/illusions_demos.html
Adelson, E., 2000. Lightness Perception and Lightness Illusions
http://persci.mit.edu/people/adelson/publications/acrobat/gazzan.pdf
Lightness Perception and Lightness Illusions (interactive movies based on Adelson paper)
http://web.mit.edu/persci/gaz/gaz-teaching/index.html
The checkerboard shadow illusion:
http://web.mit.edu/persci/people/adelson/checkershadow_illusion.html
Some more illusion sites:
http://www.sandlotscience.com/
http://www.cogsci.uci.edu/personnel/hoffman/illusions.html
http://www.illusionworks.com/
http://www.brl.ntt.co.jp/IllusionForum/basics/visual/index-e.html
http://dragon.uml.edu/psych/illusion.html
http://www.exploratorium.edu/exhibits/f_exhibits.html
http://viperlib.york.ac.uk/browse-illusions.asp
http://www.optical-illusion.org/
http://psy.ucsd.edu/%7esanstis/SASlides.html
http://humanities.lit.nagoya-u.ac.jp/%7eillusion/gallery/NVEG/index_e.html
http://www.at-bristol.org.uk/Optical/
http://www.scientificpsychic.com/graphics/
http://www.ski.org/Vision/Fun/Illusions/index.html