Does anyone know of a program that will automagically graphically map out a network? If need be, it can be Windows based. Bonus points if its cross-platform.

Couldn't find anything automatic but these seem to be able to do it manually:

http://www.smartdraw.com/specials/network.asp
http://www.pacestar.com/lanflow/index.html

This was the first thing that came up on Google for me:

http://www.neon.com/LSwin.shtml

It runs one Windows. It is a little pricey, but might be worth checking out the 30 day trail.

they have a mac version too... i've been using it for ages ^^