windows 7 - How can I find out what's uploading traffic to the internet?

Some program I'm running is constantly uploading to the Internet. It's uploaded 300MB in the last few hours. I could reboot and see if it stops, but I'd prefer to find out what it is if possible. I've tried using the resource monitor but it's totally nonsensical - even if I run a broadband speedtest, it barely registers any traffic.

Ideally I'd like to find a tool which can tell me the current bandwidth of each application. I think NetLimiter used to work on XP but it's not supported for Windows 7.