George Ou covers how to do a WLAN site survey with a number of tools, including Netstumbler and Airmagnet survey. He also covers the proper usage and importance of a spectrum analyzer to a proper WLAN survey. In the end you get what you pay for. The commercial software is easy to use and has more features, but using his included excel macro with Netstumbler you can have a very comparable and free site survey tool.
Via [zdnetasia.com]