Is there a program or a service I can run that will monitor my total bandwidth use over a period of a time?

My problem is that I rent a dedicated server, and I have a limited amount of total bandwidth I'm allowed to use per month. The company doesn't provide me with information on how much bandwidth I'm using in a control panel, so want to find a way to monitor it myself. Mainly because if I go over the allowed bandwidth amount they'll slap me with a hefty fee, and lately I know I've been coming pretty close to using it all.

I use gkrellm. It's not the most fancy looking applet, but it can monitor pretty much anything. I've never tried, but it's probably possible to get it to shut down your network connection when you reach a certain limit.

Oh my mistake, I should have specified that the program needs to either be viewable from the CLI or via a webpage. The server isn't running X at all.

Although this is not ideal, I have found it to work:
If you run ifconfig, you will notice that it gives you the amount of data transfered (in two parts, RX and TX, for received data and transmitted data, respectively) since the last reboot. If you were to write this value down at the end of every month, and subtract the current value from the recorded value, it would tell you the amount of data transfered during that month.

So you want to monitor the server from another computer? I think perhaps gkrellm can do that to. Or you could try ntop. There everything is displayed and configured through a web interface, although it might be a bit bloated for your needs.

EDIT: Found an article regarding gkrellm-server here: http://www.stearns.org/doc/network-m...ng.v0.1.1.html