Internet Monitoring Software

Hey

I'm looking for a program to monitor my internet usage. I don't mean something like NetNanny, but a (preferably free) program which monitors how much data my programs are downloading.

This is because recently I've been having unusually large amounts of data downloaded under my ISP account. I want to monitor how much data my programs are downloading so I can see how often they check for updates etc.

Does anyone know of software that can do that?

Cheers