Back on October 8th, I made a post regarding a Virtual Beta Exam, 70-113 (http://blogs.technet.com/haroldwong/archive/2008/10/08/new-virtual-lab-based-exam-70-113-windows-server-2008-ad-configuring.aspx). In that post, the deadline for taking the exam was pretty much the end of October. I had quite a few emails from folks asking me very similar questions so I made an updated post on October 15th (http://blogs.technet.com/haroldwong/archive/2008/10/15/update-to-virtual-lab-exam-70-113.aspx).
I did find out recently that the beta has been extended to December 17th. And before you ask, No, we have not reached the 3000 participant level yet so you can still get the three free exam vouchers!
Since it does seem testing centers are filling up their available test seats quite quickly, I would encourage you to go register as soon as possible to get your seat now.