Here's a Friday Virtual Field Trip to amuse and distract you from all those things you really should be doing: http://www.happyplace.com/9574/grammar-test-keeps-idiots-off-of-the-internet
I'm thinking a grammar test could be useful for a lot of purposes...at the DMV for starts. Imagine how much more smoothly traffic would move if everyone on the road knew the difference between its, it's and itch.
And if you still haven't wasted enough time, there are always absurd warning signs... http://www.happyplace.com/4042/most-absurd-warnings-and-product-disclaimers
What did we do before the internet, anyhow?