inSSIDer is free, open-source Wi-Fi scanning software.
* Compatible with Windows XP, Vista and 7 (32 and 64-bit)
* Uses the Native Wi-Fi API and your current Wireless network card
* Sort results by MAC Address, SSID, Channel, RSSI and "Time Last Seen"
* Compatible with most GPS devices (NMEA v2.3 and higher)
* Inspect your WLAN and surrounding networks to troubleshoot competing access points
* Track the strength of received signal in dBm over time
* Filter access points in an easy-to-use format
* Highlight access points for areas with high Wi-Fi concentration
* Export Wi-Fi and GPS data to a KML file to view in Google Earth.
* Filter through hundreds of scanned access points