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.
SevOne - SevOne provides network managers with monitoring, troubleshooting, and performance reporting capabilities.
Pandora FMS - Pandora FMS: Opensource monitoring software
Flowmon - Clever Network Monitoring and Security Solution based on NetFlow, IPFIX and Network Behavior Analysis
cStatus - Monitor and scan a network.
OpenNMS - Project home page of OpenNMS - a java based network managememnt platform developed under the Open Source model