Fping (open source) - fping is a program to send ICMP echo probes to network hosts, similar to ping, but much better performing when pinging multiple hosts.
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).
NetTK - NetTK, Network Tool Kit, is an Open Source alternative for monitoring and troubleshooting your...
TCP Optimizer - SpeedGuide.net - The Broadband Guide. Cable modems, DSL, Wireless, Network security. Free speed tweaks and TCP/IP tools for optimizing system performance.
PingDoctor - PingDoctor is software that is considered to be the most powerful and easiest to use network route analyzer.
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.