Got an hour to kill? xkcd.

Normally, xkcd.com is a quick cartoon that is very intellectual in a delightfully warped sort of way.  This time, however, Randall has created the largest comic I've seen in years.  Called "Click and Drag", it's a big worl to explore. You could take as long as a couple of hours to see it all.

http://xkcd.com/1110/

Here's a sample image:

It's waaaaay underground. Go find it.

But grade your homework papers and tests first.