The current issue of the c't magazine
features articles about improving the wifi signal at home. They cover a Windows tool called inSSIDer, which shows the wifi signal levels on the channels 0-13.
However, there's no such tool for linux. I came up with a simple solution in python, which parses the output of iwlist scan. This file
is tested on Ubuntu 11.04, this one
runs on Ubuntu 11.10. Both scripts can be executed like this:
watch 'sudo iwlist scan | python wifi-graph-*.py'
This is a quick hack, but it works great for me. Feel free to improve the scripts! Update: Fixed the link to the second file. Update 2: I've created a git repository. Please file bugs there. If you have different solutions, a graphical interface, bugfixes or whatever, feel free to provide patches!