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. It runs on Microsoft Windows 98 and above. A trimmed-down version called MiniStumbler is available for Windows CE.
NetStumbler is commonly used for: Wardriving, verifying network configurations, finding locations with poor coverage in one’s WLAN, detecting causes of wireless interference, detecting unauthorized (”rogue”) access points, aiming directional antennas for long-haul WLAN links
Kismet is an 802.11 layer2 wireless network detector, sniffer, and intrusion detection system. Kismet will work with any wireless card which supports raw monitoring (rfmon) mode, and can sniff 802.11b, 802.11a, and 802.11g traffic.