I use pfSense, that has the ability to graph traffic, packets, ping times, and real-time usage (e.g. 15.51 Mbps down, 1.32 Mbps up) in a nice graph too. Google up pfSense for further details on it. It's basically a FreeBSD based router firmware, but very sophisticated and advanced, and I currently use it instead of the Business Hub 3 that BT supplied as I'm able to setup QoS as I want, not how the Hub would want.
I think there's a tool called cFos Speed or something like that, perhaps someone else can clarify. It's a Windows application for monitoring usage.