Microsoft is offering developers $100 for each Windows 8 and Windows Phone 8 app written between March 8 and June 30, 2013. Participants must be over 18 and live in the US. Up to ten Windows 8 apps and ten Windows Phone 8 apps per developer are eligible, which makes it possible to earn up to $2000.
NOTE that developers must pay a fee of $49 per year for individuals and $99 per year for companies to list apps on the Windows Store, so that fee will come out of the first app.
Read further and detailed Terms and conditions here.
This is the link to Sign Up for the Program.
Interesting in writing a Windows 8 or Windows Phone 8 app? Download Visual Studio 2012 and tools here – Windows 8 Tools