Closely related to E2: Perception of Stimuli, but immensely enjoyable on any occasion, illusions are your mind messing with you. Or are they? Here are some great collections.
The peer-iodic table of illusions, from NewScientist.com
Optical illusion collection from eChalk
MOIllusions – mighty optical illusions blog
Gravity-defying ramp wins illusion contest, from Nature
Illusion contest, from NeuralCorrelate
The ‘blue’ and ‘green’ are the same colour!
In this article from NotExactlyRocketScience, Ed Yong explains that the size of your brain’s visual cortex (which is incredibly variable between people), affects how you see the world – including how likely you are to fall for optical illusions.
Stare at the centre and then see what happens to the Moon!
Are these dots really moving? Find out at moillusions.
The next two are after-image illusions:
This one was tweeted by @StephenFry: