Another app I really like is Wifi Analyzer.
It's been a long time since I set up my network, and over time the competition for bandwidth has grown. From time to time, channels have become crowded. We would adjust channels and antenna placement by trial and error.
How nice it would have been to have had this app. Wifi Analyzer is just delightful. It graphically shows the signals it finds, what channels they are on, and how strong they are, and it is just great to be able to walk around with the phone and see it all. And it's free.
Check out the sceenshots and reviews at: https://market.android.com/details?id=com.farproc.wifi.analyzer&hl=en