It turns out my home phone number can be reached for free over the Internet thanks to SIPphone. I live in Student Family Housing at BYU. We have an analog phone but the whole system is backed by a SIP-based VoIP system. Apparently the University has a peering agreement with SIPphone. Not only can we be called over the Internet but we can call a variety of SIP networks from our analog phone. But it gets even better. This VoIP thing opens up a huge number of possibilities.
SIPphone offers conference lines. These can be accessed via SIP by anyone, anywhere (and by myself and some other lucky souls from an analog phone). They don't have any passcodes or anything so there's no security but there are 10,000,000 possible lines so as long as you've picked one nobody else is using you should be fine.
IPKall offers a free phone number (Washington state area codes only) which will forward to any SIP URI you want it to. I'm not joking. I have an area-code 360 phone number that calls my computer. It's possible that this kind of thing will spread to other areas than Washington but for now you can take comfort in the fact that most people have free long-distance in the US of some kind or other.