Monitor your Router with Cacti
Devices attached to your router in some way — whether wired or wireless, use bandwidth on your network. Most homes have plenty of devices that are always connected and some of which connect periodically (Xbox, Wireless printer, etc.) Cacti is a tool for monitoring, amongst other things, network usage. There are other tools for the job (mrtg, AirPort Utility, etc.,) however, Cacti feels the best...