The second largest DSL provider here is Free. DSL2, fiber-to-home, TVoIP, so many cool things that I am an happy customer. They also have a "shared" VoIP service : if you enable the "freephone" service in your own freebox, then with a compliant wifi-based phone, you can connect to ANY freebox in the country to make a call. Basically, you accept to give a very light bit of your bandwidth so you can use others' bandwidth too for free phone calls (FON does it too).

They just announced a VoIP app for iPhone and iPod Touch (page in english) !!! With that app, and if you're a Free customer, you can make free phone calls to all landlines in the country and 69 other countries ! Wow. The iPod Touch goes iSIPhone :-)