I recently came accross this really rather nifty speed test tool made by some guy called Jack Dinn, it measures at set intervals the up and down speed of your broadband connection and display nice averages.
I have run it in the background for a little over a day on my work connection and the traffic differences are really notable. It is in an office with about 30 plus people in it and it a web dev company (with a shitty 2 meg leased line).
I am going to run it for a while at home on my 50 meg at home to see how it goes.
here is the resulting graph for work.
