At SIGIR Microsoft showed off their Page Hunt game. Page Hunt is in the same vein as GWAP by Luis Van Ahn. The game in short: Guess the query given a web page. If the page is returned in the top 5 results by Bing, you win and get points.
If you didn't play it at SIGIR, give it a try.
It's a cute game, but I'm not sure about its real utility or long-term re-playability.
Here's my quick tips:
Homepages - homepages are pretty easy, the title usually works.
Detailed pages - Pick what you think will be an infrequent phrase from the page and search for it with quotes. It almost always works. There's no incentive to issue shorter queries for higher points.
Post your top score in the comments.