Free tools like Xirrus Wi-Fi Inspector and the Xirrus Wi-Fi Monitor Gadget for Windows 7 with links to other third-party systems/network admin tools. Very cool!
"Ekahau HeatMapper is a free software tool for quick and easy coverage mapping of Wi-Fi (802.11) networks. It's the only free, easy-to-use tool that shows, on a map, the wireless network coverage in your home or small office. HeatMapper also locates all access points."
In addition to the free software, paid laptop and portable versions are available, with and without wireless cards and other hardware.
"With Connectify you can share expensive airport Wi-Fi with co-workers, create a wireless hotspot in your ethernet-only hotel or dorm room, even extend the range of your home router."