I've drafted up the first version of my certification learning plan in Visio. My next exam will be 70-236 just because I love Exchange. After completing that exam I will be a MCSA on 2003 Server and a MCTS on Exchange 2007. I have to complete 3 more exams after that to complete my MCSE.
Then, I will move onto either Windows Server 2008, Windows Vista or back to Exchange Server. It all depends on where my career goes and what operating systems and server software I end up working on. I'm also interested in picking up some SharePoint Server certifications, but I guess it will have to wait. It would be good to have my MCSE complete by the end of the year (so much for June).
Anyways, have a look at my certification plan below: