FastNetMon - FastNetMon is a very fast DDoS analyzer with sflow/netflow/mirror support.
Nfsen - NfSen is a graphical web based front end for the nfdump netflow tools that allows you to:
NetVizura NetFlow Analyzer - NetFlow Analyzer is a solution for bandwidth monitoring and traffic analysis. It helps with traffic investigation, analysis and reporting
Arbor - Easily manage product development
Zabbix - Track, record, alert and visualize performance and availability of IT resources
LibreNMS - A fully featured network monitoring system that provides a wealth of features and device support.