Nmap - Nmap Free Security Scanner, Port Scanner, & Network Exploration Tool. Download open source software for Linux, Windows, UNIX, FreeBSD, etc.
inSSIDer - inSSIDer Essential makes it easy to maintain small business WiFi.
SolarWinds Network Configuration Manager - SolarWinds is a leading provider of powerful and affordable IT infrastructure management software. Make IT look easy.
NetSpot - NetSpot is a free app for wireless site surveys, Wi-Fi analysis, and troubleshooting
Cisco Network Assistant - Cisco Network Assistant simplifies wired and wireless network management, and provides critical product information using Cisco Active Advisor.
Homedale - With Homedale you can search for Wi-Fi / WLAN Access Points and monitor their signal strength.