Scaled Composites has claimed the Ansari X-Prize today with SpaceShipOne's second successful flight in two weeks, so it's fitting to think about some other similar prizes that could usefully stimulate the advance of technology and/or civilization more generally. If you had the money, what type of prize would you set up? Personally, I want an affordable flying car. I'm sure I can think of something better in a few minutes, and I'll update this post when I do. Remember, there's no point in making a prize for something that's already likely to be incredibly profitable, like developing a cure for cancer.