Wireless Network Watcher - scans your wireless network and displays the list of all computers and devices that are currently connected to your network.
TamoGraph Site Survey - Wi-Fi site coverage survey and modelling application
inSSIDer - inSSIDer Essential makes it easy to maintain small business WiFi.
Waircut - Free network audit app
Aircrack-ng - Aircrack-ng is an 802.
Homedale - With Homedale you can search for Wi-Fi / WLAN Access Points and monitor their signal strength.