The Dude - MikroTik is a Latvian company which was founded in 1996 to develop routers and wireless ISP systems. MikroTik now provides hardware and software for Internet connectivity in most of the countries around the world.
Pandora FMS - Pandora FMS: Opensource monitoring software
SolarWinds Network Bandwidth Analyzer - Download a 30-day free trial of Network Bandwidth Analyzer Pack, easy-to-use software that delivers real-time monitoring, alerting, and reporting for routers, switches, and other SNMP-enabled devices.
cStatus - Monitor and scan a network.
Flowmon - Clever Network Monitoring and Security Solution based on NetFlow, IPFIX and Network Behavior Analysis
Zabbix - Track, record, alert and visualize performance and availability of IT resources