Eyetricks.com  
   Collection of illusions and other mind teasing oddities. Includes illusions that you can make.
   http://www.eyetricks.com/

Akiyoshi's Illusion Pages  
   Includes anomalous motion illusions.
   http://www.ritsumei.ac.jp/~akitaoka/index-e.html

The Exploratorium's Online Exhibits: Seeing Exhibits  
   Interactive illusions from the exploratorium.
   http://www.exploratorium.edu/exhibits/f_exhibits.html

Colorcube  
   Illusions organized by category, including blind spot, blink effect, bordering, chromatic adaptation, colorblindness, and others.
   http://www.colorcube.com/illusions/illusion.htm

Magic Eye Image of the Week  
   Includes a new image every week demonstrating stereograms.
   http://www.magiceye.com/3dfun/stwkdisp.shtml

Sandlot Science  
   Interactive optical illusions, games, science projects, fun puzzles, and distortions.
   http://www.sandlotscience.com/

Illusion Works  
   A multimedia museum of optical and sensory illusions, with on-line demonstrations and explanations.
   http://psylux.psych.tu-dresden.de/i1/kaw/diverses%20Material/www.illusionworks.com/

M.C. Escher  
   Optical illusion art, news, history, copyright and foundation information.
   http://www.mcescher.com/

Counter-Rotating Spirals Illusion  
   Java applet, including other illusions, such as an animated Necker cube.
   http://dogfeathers.com/java/spirals.html

NIEHS Kids Page -- Optical Illusions  
   Presented by the National Institute of Environmental Health Sciences. A collection of illusions.
   http://www.niehs.nih.gov/kids/illusions.htm

Eye Magic  
   Collection of high quality optical illusions that come with clear explanations.
   http://www.harmsy.freeuk.com/opticalillusions.html

Eluzions' Optical Illusions  
   Contains many optical illusions, illustrating a wide range of visual anomalies and surprising optical effects. A free screensaver, posters, and educational explanations are also provided.
   http://eluzions.com/Illusions/

Crazy Images  
   Interactive animations and optical illusions that respond to user's input.
   http://www.crazyimages.com

Eyetricks.com: Optical Illusions  
   Collection of optical illusions, brain teasers and games.
   http://www.eyetricks.com/illusions.htm

Khushboo's Virtual Escher Gallery  
   Small selection of images by the artist.
   http://www-scf.usc.edu/~khushboo/escher/index.html

Visual Phenomena and Optical Illusions  
   Interactive illusions, including Benham's disk and other illusions involving motion.
   http://www.michaelbach.de/ot/

Optical Illusions  
   From the Department of Ophthalmology and Visual Science at the University of Illinois, a collection of illusions and after images.
   http://www.uic.edu/com/eye/LearningAboutVision/EyeSite/OpticalIllustions/index.shtml