The MCTS 70-599 Pro , a certification exam for the windows phone 7 developers on designing and developing windows phone applications is now available in the prometric testing centres .
As per the Microsoft Learning site , the Published date is still July 14 , 2011 ( In development ) .
But looks like the 70-599 is already made available
MCTS 70-599 is designed to test the candidate’s knowledge and skills on designing and developing applications for the Windows Phone platform.
Note : The candidates who earn the MCPD: Windows Phone Developer certification will be required to show continuing ability to perform in this technology area by completing a recertification exam every two years.
More info on the exam can be found here
Visit Prometric site or center to register for the exam