Yes they do.
Heres the one experience I had with it.
I had a apple base station ( graphite for reference).A co-worker had a 2.4 ghz cordless phone, whenever she turned it on. The signal on the airport would basically die. I tried changing channels on the airport and the phone but it only helped to a certain degree, the longer she stayed on it would get worse and eventually just die off.
We replaced the cordless phone with a 5.4 ghz phone and all our problems went away.
Hope this helps, I'm sure Jack/Spidey or Scott could explain this better.