Wireshark - Wireshark is a network protocol analyzer for Unix and Windows. It lets you capture and interactively browse the traffic running on a computer network.
Vistumbler - Vistumbler is a wireless network scanner for Windows Vista and Windows 7. Features:
netcat - Netcat is a featured networking utility which reads and writes data across network connections...
inSSIDer - inSSIDer Essential makes it easy to maintain small business WiFi.
tcpdump - tcpdump is a common packet analyzer that runs under the command line.
NetSpot - NetSpot is a free app for wireless site surveys, Wi-Fi analysis, and troubleshooting