Well, here is just the right tool for monitoring all data in and out of your PC through the internet connection. Best thing about it is that it is open source and all free without any adware or sharewares coming bundled with.
So what is it? It is called BitMeter 2. Some of the features I found very useful are that, it can visually show all data in and out live, as well as historical data based on time, be it hourly or daily and it can be set to alert you when, a certain usage limit is reached. Depending on the service your ISP is providing, you might have a usage limit per month. So, it is a good thing to know exactly when your data usage [total downloads/uploads] limit is going to reach before the month ends and how much data usage is remaining in a very convenient way.