Get Detailed WiFi Info From the Menu Bar
You can retrieve extended wireless connectivity data from anywhere within Mac OS X by holding down the Option key and then clicking on the WiFi menu icon.
Option-clicking will display a sub menu under your active wifi connection that shows what wireless band you are using (PHY Mode), the routers SSID (BSSID), what channel the wireless router is using, which encryption method (Security), signal strength (RSSI), the transmit rate, and MCS index (whatever that is).
You can also mouse-over other SSID’s to see a slightly more condensed version of this information. All of this can be helpful for avoiding potential channel conflicts, or when troubleshooting wireless problems.
And yes, I called it the WiFi menu rather than AirPort, since Lion is moving away from the AirPort references, at least in regard to the menubar.