I found this fantastic network-sniffer. It's so good I didn't even know there were programs like it. It's called Iris from eEye Digital Security. It will sniff all packets from a network, and then decode the packets. That means if anyone on the network is surfing the net, the sniffer will show the same web-pages in a window. Or you can see the HTML, if that's what you want. I'm using it to look at XML being sent across the network, and it totally does the job.
As you can all understand, I'm very excited about this product. It's a 10 out of 10 on my scorecard!