Graphically See Your Home Network With jNetMap (Win/Mac/*Nix, FREE)
And for that purpose, jNetMap is an excellent crossplatform tool.
Sure, if you're on *nix or a Mac, you can probably use
nmap -sP 192.168.1.0/24
to see a raw version of what's going on. But does that have the same impact as this:
I had to move some of the connections (it didn't recognize my stupid desk hub for example, and put all the wireless connections to jillboot), but for the most part it makes it easy for me to see what connects where.
There are all sorts of plugins so that you can use this tool for a lot more, but the base functionality is great for making sure your basic network layout is the way you want it to be, and keeping track of your devices.
And yes, there's a marsupial theme. Because WOMBATS.
jNetMap is free crossplatform software - (Win/Mac/*nix) available at Sourceforge.