Like.com is pretty cool. It tries to help you shop for things based on physical similarities, they've got a neat image recognition thing going. I was surprised when I saw it actually work.

Also cool is Shazam Entertainment's music recognition software. http://www.shazam.com/music/portal/template/pages/p/company_...

Apparently, if you hear something on the radio or whatever, you dial up shazam and they can tell you what it was. Magic, I tell you.

Then there's Heroku, which is kind of 'wtf amazing' to me.