InSSIDer is a relatively new open source Wi-Fi stumbler developed by MetaGeek, the maker of the Wi-Spy spectrum analyzer. It shows the usual list of AP details, but doesn’t show the exact authentication method. You can see the encryption method used but can’t distinguish, for example, between WPA-PSK and WPA-Enterprise networks. Like most other stumblers, inSSIDer doesn’t include the noise or signal-to-noise (SNR) values; just gives you the RSSI values.
However, it features very intuitive graphs. The time graph shows the signal levels (in dB values) of each AP for the past 5 minutes. Then there’s a graph for each 2.4GHz and 5GHz channel, showing the current signal levels and channel width usage of each AP. Another useful feature: the filters enable you to filter out APs based upon the AP’s band, channel, signal, security, and age status—great if you have a large amount of APs to deal with. It also features GPS support and lets you export to Google Earth.