Monitoring Users on your home network?

prowdtobebrown writes: Is there any way to monitor the network usage of users on your home wireless network? I'm living in a house with a bunch of guys (9 of us in total) so bandwidth sharing over a normal comcast cable line is a major issue. If someones hogging bandwidth downloading movies (which we don't want them to do for potential legal reasons as well) it would definitely help to know.