Wayne has written up some impressions, tips, and related resources for these exams; I'm sharing them here in case any of these are on your list and migth be helpful, if you'd like to check them out. Thanks Wayne.

70-620: Vista "...Anyone who has spent a good deal of time with Windows XP Professional and been subject to 70-270 in the past will have a real head start on this exam. Really, I found the best way to study for the exam was simply to work on vista in 32 bit and 64 bit for a couple months. Connect to wireless networks at home and in an airport, etc. Configure and connect a VPN. Enroll the computer with a client computer certificate and a user certificate. Run some programs on the computer. Make a backup of your computer using the windows backup utility..."
70-238: Exchange 2007

70-237: Exchange 2007
70-236: Exchange 2007
70-299: Implementing Security on a Microsoft Windows Server 2003 Network
70-298: Designing Security for a Windows Server 2003 Network
70-294: Planning, Implementing, and Maintaining an Active Directory Infrastructure for Windows Server 2003 Exam
70-293: Preparing and Maintaining a Windows Server 2003 Network Exam
70-291: Implementing and Managing a Windows Server 2003 Network Exam
70-285: Designing Exchange Server 2003 Exam
70-284: Implementing / Managing Exchange 2003 Exam
70-290: Managing and Maintaining a Windows Server 2003 Environment Exam
70-270: Windows XP Professional Exam

OT: Did I tell you I won a Zune? We had a team party/thing at this video game place in Seattle (that's right, you are waiting on exam results, welcome kits, and more exams with simulations, and we're sitting around drinking beer and playing video games every day. sick! it's sick.) But in any case, that is, actually, what we were doing one afternoon last week and there was a contest, and my class-act team, with the class-act name of Silent But Deadly, won and there was a prize, so now I have a Zune.