Doesn't exist. Someone would have to provide the phone line and therefore get paid. How else could you connect? Unless you stole the wireless connection from someone else and if you did this and were caught you would be prosecuted.
If you live in an area covered by one of the media companies you can get deals where if you take on a package you are getting such a good deal you effectively get your line rental or whatever for free. A friend of mine has an Orange mobile phone and gets his internet for free, but does still pay for his phone line though.