In a nut shell, you could win $50,000.00 as the grand price, many other $10,000.00 prizes, and 1 of 10 iPad’s just for registering!
If you’re a developer, or have friends who are developers you can convince to work with you, or want to learn to code then you should definitely look at the PayPal X Developer Challenge web site.
If you want some more information you may want to visit the Paypal and Yahoo Developer Challenge demo evening on Tuesday the 20th of July. It is being held at TechHub in London. The event is a great way to learn about the PayPal and Yahoo technologies available, and the competition.