They will also give you a Windows Phone 7 device for free. Of course, you have to make something for Microsoft, too - there is no free lunch :)
Microsoft announced their contest named "Hey Windows Phone, I need this app". If you have a great idea for a smartphone application, but you don't have the skills or connections - this contest is just for you! Microsoft will hear your ideas. If they like it, they will develop and release it and you will be 5000$ richer with a new Windows Phone 7 phone :)
The contest has started today and will be closed on 8th of July 2010. So you have a month to think. Stop browsing and get thinking now!
Here is the official page of the contest.