""Anti-Gravity Hills" (also known as "Gravity Hills", "Spook Hills", or "Magnetic Hills") are natural places where cars put into neutral are seen to move uphill on a slightly sloping road, apparently defying the law of gravity. Typically, the "spooky" stretch of road is rather short (50-90 m), only a few meters wide, and surrounded by a natural hill landscape, without nearby buildings. Such places are found in several countries all around the world, and have been tourist attractions for decades. They should not be confused with the "Mystery Spots" [previously] found in amusement parks. These are generally tilted cabins, purposely built as such; a person walking inside feels disoriented, getting a very strong impression of standing at an angle in a perfectly normal room." CSICOP and Discovery News explain the phenomenon, and here's the paper on which the CSICOP article was based (PDF).
posted by cog_nate on Oct 29, 2009 - 41 comments

John Thurlow's Web Sites for Kids & Teachers. The Thinking page of this treasure trove of kid-safe sites includes links that are also appropriate for adults who just like to play around, such as Funderstanding's Roller Coast Simulation, and Lightness Perception and Lightness Illusions. [more inside]
posted by cybercoitus interruptus on Jan 17, 2009 - 2 comments

Blind Spot Optical Illusions. Online seminar from McCormick Lab at Yale lets you find your own visual blind spots. After that, you can make Monet's sun, and Van Gogh's ear, disappear. [more inside]
posted by cybercoitus interruptus on Jan 11, 2009 - 15 comments

More good stuff for people who like visual ("optical") illusions (previously): A nice Scientific American article, a particularly creepy illusion, and a link to the "Best visual illusion of the year" contest. Given that the eye/mind/brain is so easy to trick, a person might wonder what's really out there in the world.
posted by cogneuro on Aug 28, 2008 - 26 comments

Optical illusions and why they look that way.
posted by OmieWise on Jun 16, 2008 - 26 comments

10 optical illusions in 2 minutes - SLYT, Samsung promotion.
posted by fearfulsymmetry on May 15, 2008 - 19 comments

The predictably irrational door game. [more inside]
posted by Rumple on Feb 22, 2008 - 39 comments

Motion induced blindess. Be sure to check out the other really cool stuff
posted by elemenopee on Apr 18, 2005 - 20 comments

You got me trippin.' For those of you who miss some of the visuals of controlled substances. Not high-tech, but some fun candy.
posted by datawrangler on Jul 4, 2003 - 10 comments

These links are probably best viewed only by the blind.
posted by crunchland on Jan 8, 2003 - 32 comments

M.C. Escher + Lego = ? I used to make spaceships and houses with my Lego not 3D representations of famous optical illusions! [via Filepile]
posted by bhell13 on Oct 7, 2002 - 29 comments

A professor of vision science at MIT understands that life isn't just black and white, even though we often see it that way. This amazing illusion proves it, and these slick, fast-loading, Flash demonstrations of lightness perception show how it's done. (My favorite is the "Koffka Ring".) White paper here, for deeper background.
posted by taz on Sep 27, 2002 - 29 comments

I'm usually not a big fan of optical illusions (unless there's a nice magic trick built around it), but this one is pretty brain-burning. (Yes, that's my entire front-page post. But hey: at least it ain't a news story.)
posted by Shadowkeeper on Oct 18, 2001 - 29 comments