Spiceworks Help Desk - Help desk software features that work for IT
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).
Spiceworks - Spiceworks bundles network monitoring, helpdesk, UPS power management, PC inventory tools, an online community, and much more for free
TCP Optimizer - SpeedGuide.net - The Broadband Guide. Cable modems, DSL, Wireless, Network security. Free speed tweaks and TCP/IP tools for optimizing system performance.
Paessler PRTG - An advanced network monitoring solution to monitor network up/downtime, traffic and usage.
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.