I've have good luck with Panasonic. I've currently got two different 2.4GHz Panny systems in my house - one older single handset system with answer machine, and one newer dual handset system that could handle a third phone. Although they don't integrate into one cohesive system they do interoperate well without interference. (I still need to use both base stations, and picking up a newer handset wont automatically kill the answer machine if it's already picked up - I'd have to 'flash' the line).

I also haven't noticed any problems with my 802.11b network either. I occassionally get intereference from my neighours two doors up the road (really should change my channel!), but never from the 'phones. My inlaws have a Uniden that would kill their 802.11b network the moment they used it. Even when I tried different network channels the issue didn't disappear completely.