Zabbix - Track, record, alert and visualize performance and availability of IT resources
Technitium MAC Address Changer - Technitium MAC Address Changer (TMAC) is a freeware utility to instantly change or spoof MAC Address of any network card (NIC).
Paessler PRTG - An advanced network monitoring solution to monitor network up/downtime, traffic and usage.
TCP Optimizer - SpeedGuide.net - The Broadband Guide. Cable modems, DSL, Wireless, Network security. Free speed tweaks and TCP/IP tools for optimizing system performance.
Observium - Observium
Axence netTools - Axence netTools is completely free of charge, both for home and commercial use – all you have to do is to register. A tool for professionals – and others.