NetStumbler
NetStumbler is a Windows utility for 802.11 wireless network auditing. Vesion 0.4.0 is the long-awaited new release that supports more cards than ever and even includes help!
MiniStumbler
NetStumbler for your PDA! MiniStumbler 0.4.0 now works on most (but not all) Hermes, Prism and Atmel chipsets, including some CF and SDIO card
Look@LAN
Look@LAN Network Monitor is an advanced network monitor, that is easy to use and automatically detects and analyzes your network nodes, including operating system. The program can monitor the nodes and alert you of any changes (new nodes, offline nodes etc.). The main window lists all available nodes and detailed statistics and scan results are available for each individual machine, including a real-time traceroute report, ping results, active services (open ports) and more. In addition to the auto-detected nodes, you can also customize the scan ranges and add additional networks. Additional features include HTML reports, statistical graphs, network tree view, single node scanning and more.