This site probably isn't technically useful, but it is fun. We had a massive Sporcle fad at school over the last couple of years, where almost every PC had somebody on it. The school didn't ban it for so long because it isn't a gaming website, in fact, it's more of a knowledge website. Teacher's would even start playing it with us in class.
The site is all about filling in lists. The most popular are name the 50 US states, you are given a time limit and off you go. Their are thousands of different ones to chose from and it is incredibly addictive. From characters of TV shows to countries of the world. If you complete countries of the world, you are a God by the way. Don't forget Micronesia!
If you're bored, check it out, and think of it as being productive.. you're using your brain and learning stuff.