I like to think of messaging systems as living entities rather than a random collection of servers passing round email. Proof of this is that while working in Microsoft Consulting Services, we had a client run Exmap only to discover that his 'simple messaging infrastructure had sprouted children in the background. He then remembered adding a number of servers in the past but forgotten about, says something positive about how low maintenance Exchange can be.
It appears over the holidays we released a stencil for Visio to include shapes for Exchange Server 2007. Next time the boss pops round to your desk and demands to know more about the companies messaging infrastructure, you can divert his attention to a detailed diagram up on your wall and ask him to come back with questions once he has finished absorbing the information ... by which time you would have slinked off to get yourself a coffee :-)