They might... actually it's more likley that your wireless net will interfere with your phones. Have you ever tried using your phone and your microwave at the same time? Try it... if you get static it means that your phone is susceptible to interference, and could very well receive similar interference from an 802.11b network.
I have a cybergenie phone system that runs on 2.4GHz, and if I'm downloading a lot through the wireless connection I get pretty constant pops and clicks in phone calls... pretty annoying but I've come to live with it. As soon as 802.11a is cost-effective I'll switch to that because it uses 5GHz, hence avoiding the microwave and cordless phone interference problems.
l2c