Cool Site: Farecast - predict when to buy airline tickets!
This is the travel site I've been wishing for! Have you ever wondered whether you should buy airline tickets now or wait? Well, now Farecast tries to help you out by predicting for you. It looks at historical patterns to recommend flight ticket purchases. Currently, it's in beta, and only covers the some common destinations. Hopefully they'll have full global city coverage soon!
They also have a blog.