Vistumbler is an open source Windows application that finds Wireless access points - Uses the Vista command 'netsh wlan show networks mode=bssid' to get wireless information. It displays the basic AP details, including the exact authentication and encryption methods, and can even speak the SSID and RSSI.
It also displays graphs of signal levels. It's highly customizable and offers flexible configuration options. It supports AP names to help distinguish them, also helping to detect rogue APs.
Find Wireless access points - Uses the Vista command 'netsh wlan show networks mode=bssid' to get wireless information
Export/Import access points from Vistumbler TXT/VS1/VSZ or Netstumbler TXT/Text NS1
Export access point GPS locations to a google earth kml file or GPX(GPS eXchange format)
Live Google Earth Tracking - Auto KML automatically shows access points in google earth.
Speaks Signal Strength using sound files, windows sound api, or MIDI
Open Source (GPLv2 License / Written in AutoIt Scripting Language)