Since I’m not familiar with Visio, I’m not sure what its capabilities are – so I don’t know if this will be way too rudimentary to be useful. But I’ve used Dia for flowcharting and the like and I know they have standard Cisco icons. For actual layout, I’ve heard a lot people speak highly of GraphViz; never used it myself.
Well, that’s why I also mentioned the default packs for them, because it seems all I can find for it are crap. And a single switch/hub icon, stuff like that.
Have you gone to the equipment manufacturers’ sites? I remember when what you’re describing was a huge pain, but a lot of vendors offer the Visio stencils for free now.