Bumping Into Qwest's Invisible Cap → Excess charge and I'm out of here!

First of all, I'm probably no where near the 3GB limit as I'm not a movie/video/music streamer. As to how I would be able to keep track of my broadband usage, I haven't a clue.

However, IF Qwest ever comes around and says I'm using TOO much, I'm out of here and back to cable.

Anyone know of a utility that keeps track of usage on a home network with 4 computers accessing the internet at various times? I'm using the Qwest 3347 modem/router.