Here are some of our favorite tools for troubleshooting wireless networks.  If you are looking to track down wireless interference issues like microwaves, cordless phones, or eliminate adjacent channel interference, check out our Chanalyzer Lite software.

inSSIDer

InSSIDer is a replacement for NetStumbler that works on Windows Vista and Windows XP.  Use it to track signal strength with a client wireless card.  It is free and open source.  It includes GPS support and the ability to export in NS1 or KML.

Ekahau Heatmapper

The Ekahau Heatmapper site survey application allows the user to visualize all Wi-Fi access points and their locations.  Read a great review from Ars Technica http://arstechnica.com

XIRRUS Wi-Fi Monitoring Tool

The Xirrus Wi-Fi Monitor Widget for Windows XP provides at-a-glance access to information about all available Wi-Fi networks and your current Wi-Fi connections. It provides a useful tool for anyone deploying and operating wifi. Applications include: search for local Wi-Fi networks, verify Wi-Fi coverage, verify AP settings, detect rogue APs, locate Wi-Fi devices, aim Wi-Fi antennas. For more information, go to: http://www.xirrus.com/library/wifitools.php or view the PDF user guide accessed via the About box within the Widget.

Kismet

Kismet is a network detector, packet sniffer, and intrusion detection system for 802.11 wireless LANs. Kismet will work with any wireless card which supports raw monitoring mode, and can sniff 802.11b, 802.11a and 802.11g traffic. The program runs under Linux, FreeBSD, NetBSD, OpenBSD, and Mac OS X. The client can also run on Windows using the specialized AirPcap adapter from Cacetech.

NetStumbler

NetStumbler (also known as Network Stumbler) is a tool for Windows that facilitates detection of Wireless LANs using the 802.11b, 802.11a and 802.11g WLAN standards. A trimmed-down version called MiniStumbler is available for Windows CE. NetStumbler has issues running on Vista. An alternative is Vistumbler.

iStumbler

iStumbler is a utility to display information about nearby 802.11b and 802.11g wireless access points. It is mainly designed to be a tool to help find access points while traveling, or to diagnose wireless network problems. iStumbler can also display Bluetooth and Bonjour network information, and has a dashboard widget.

KisMac

KisMac is a wireless network discovery tool for Mac OS X. It has a wide range of features, far exceeding that of NetStumbler, its closest equivalent on Windows, and Kismet, its Linux/BSD namesake. KisMAC is no longer being actively developed.

Iperf

Iperf is a throughput application.  There is a great GUI variation called JPerf. Both allow you to compare actual throughput to the stated data rate of a WLAN.