Below is a review of the top free NetFlow collectors and analyzers available for download today. I have categorized them by who they are best suited for.

The Bandwidth Ghost

sudo softflowd -i eth0 -n 127.0.0.1:2055

Waiting for flow data...

While primarily a packet sniffer, Wireshark is an industry standard for capturing and analyzing NetFlow records to troubleshoot specific protocol issues. Why You Need a NetFlow Analyzer