http://www.neave.com/strobe/

Click start, stare at it for 20 seconds, then look around.

Endless amusement. O_O

 

Yeah these are fun but actually fairly common, the last psychology class I was in the professor had us looking at this illusion and a bunch of other ones for several days while we studied the eyes and parts of the brain.

This site has a lot more illusions along a similar vein if anyone is interested, some are cheesy but some are pretty interesting like this one and the motion induced blindness one.
http://www.echalk.co.uk/amusements/OpticalIllusions/illusions.aspx

 

This one was a real mindfuck when I first ran across it.

Edit: Oz, woah. :awesome

 

Lol I love that one, its always hilarious to see how many people totally miss that shit, there were some other great ones like these that are my favorites.
http://www.youtube.com/watch?v=vBPG_OBgTWg
Its an experiment to test these peoples awareness and its almost stunning to see them just keep right on talking.

 

Lol since you mentioned Derren Brown, here's a funny one:

http://www.youtube.com/watch?v=j25qV5RO-nU&feature=related

 

I'm not getting the mindfuck here.

 

After the timer runs out, you see a coloured building right (if you do focus on the dot)? It's actually in black and white. Dunno if you expected that or something, but it still weirds me out.

 

Not really an optical illusion, but it is a cool psychological phenominom.
http://www.youtube.com/watch?v=Ahg6qcgoay4

 

:facepalm

/filler

 

Okay, now I see it. Maybe it should stay 'stare' instead of 'look'.

 

I think the colored building kind of is a mind fuck, because the colors will stay there if you don't lose your attention. Just continue starting at the dot, and the colors will stay until you look away.

Dunno just how long they'll stay, as I'm A.D.D and end up losing my attention on the dot after 5 or so seconds.

 

For me, they stayed until the image reset back to the beginning. Pretty mind-fuckish, in my opinion.