Well, this has confused me:

Text from other website:

"This little animation is fast becoming very popular - and no wonder: when you first look at the spinning girl, her rotation is probably clockwise. But if you start to concentrate on her shadow instead, suddenly her rotation switches to counter-clockwise! It may take some time, but the moment it happens, you are going to be genuinely surprised..."

http://farm2.static.flickr.com/1223/814863839_4e46c432c3_o.gif

Anyone got any other optical illusions?