Joe commented that he uses ethereal as an aid in debugging networked applications, I’ve also used ieHTTPHeaders and I read about livehttpheaders for you mozilla users out there. ethereal is like drinking from a fire hose, you definitely need to setup filters for the data to become information. It looks almost exactly like Network Monitor, the big difference being that ethereal runs on about 23(!) different operating systems. ieHTTPHeaders and livehttpheaders is really only useful for http traffic, but are both much easier to get information out of quickly.