Check out Bondoogle, a card trick performed using Google. The trick works like so: Have the person pick a card, try to guess the card, and get it wrong. Then ask what the card was, and say "I bet Google knows what card it is". You then type into Google Images "What card did she pick?" and it returns pictures of that very card, with the name of the card in the search box.
How does it work? Bondoogle has a mirror of the Google search engine which masks what you are typing on the screen. Instead of your question, you type
/3d/, where 3 is the number on the card and d stands for diamonds, the suit. Once you have typed the second /, you will see, instead of
/3d/, the word "What". Until you type that second slash, Bondoogle will keep adding one letter at a time, up until it says "What is it that I am looking for?". When you type that second slash, everything you type is real, so, if you only type in 4 letters, you can continue to ask "What card am I thinking of, oh wise Google master?" and the only thing Google will search for is the text between the slashes.
What's more, while the script works best automating the number and suits in a deck of cards, you can type anything into either Google search or Google Images and pull off the trick. This means that you can type "/blue/s the color of my shirt?", your friend sees "What is the color of my shirt?", and Google returns the results for "blue".
Go to ipolygraph.com/google and try it out. To take the effect to the next level, Jim Bumgardner, who wrote the script, has created a Greasemonkey extension for Firefox that changes the actual Google search engine to exhibit this behavior. This means your "mark" will be very fooled by the address bar saying google.com.This is all very cool, and I'm off to fool my loved ones.