Just came across this website referred by a gr8 friend and indeed a superb website allowing you to make FLOW Charts, Organization Charts, SWOT analysis, you an architecht or just a simple guy want to design your home do it via gliffy the beauty is that you no longer need to download heavy softwares like Visio, in addition to this you don't need to sign up, just make the diagram and save on your PC :)
Don't trust me check the Network diagram here made via gliffy:
http://www.gliffy.com/examples/network-diagrams/
So have fun, web site address = http://www.gliffy.com/
Regards,
Muneeb Iqbal