Second Shot is back which gives you the opportunity to take an exam again for free if you fail it the first time. More info here:

http://www.microsoft.com/learning/en/us/offers/Career.aspx#certification

Offer details:
Dates: January 13, 2010 – June 30, 2010.

Details: You must register, obtain a voucher code, schedule, pay, and take the first and (if necessary) the retake exam before June 30, 2010.

Applicable exams: This offer applies to all Microsoft Learning IT professional, developer, project management, and Microsoft Dynamics exams, including academic exams.

Eligible countries and regions: This is a worldwide offer that is available at Prometric test centers only.