Windows Server 2008 Core
Server core is nothing new, in fact it's been out for some time but I found this handy cheat sheet from Microsoft which is helpful.
Microsoft Server Core PDF's
Recently I took the Microsoft 2008 Active Directory exam 83-640, I actually scheduled the exam for the 70-640 but looks like the 83-640 is now the standard.
The exam is now done from a virtual server where you are given a short list of tasks to complete within a amount of time. It's actually easier for me to complete than the standard multiple question exam because you can remember steps by looking around. Also amazingly enough, the help command is not disabled, which you can also use for any problems.
A few web sites have posted information about the exam, especially concerning if you make too many wrong click would that count against you or not. It turns out that no, only completling the tasks will be recorded in the final score. But a major downside, at least for my testing was the lack of any score besides my points. This doesn't allow me to go over my exam score and study on the items I need help in. The reason given by Microsoft was the testing technology was still too new. The new exam came out in early 2009 so I would guess it should have been resolved by now.
Transcender posting about 83-640 vs 70-640
ExamCollection forum post about 83-640