The Infinite Cat Project is my Useless Site of the Day!
Yes, it's a site devoted to photos of cats looking at photos of cats on a PC who are looking at photos of cats on a PC who are looking at photos of cats on a PC who are... well, you get the picture.
And you, too, can get a photo of YOUR cat on the site! Yes, add to the infinity! *G*
Not only that, but if you scroll down a bit, you get to learn about something called the "Droste Effect", and in that bit there is also a cool link to a site that does a video loop version of the Escher effect on two Escher drawings.
Yes, folks, further proof that the Internet is truly a marvelous thing - even when it's Totally Useless! *G*