Great resource for wiring up your home for VoIP, in MAKE 03 we also have a guide “One obstacle to replacing traditional phone service with Voice over IP is that for your existing home phone jacks to work, it’s necessary to make a change to your inside telephone wiring. Fortunately, this change is very easy to make. In some cases it’s as simple as removing a plug from a jack. Still, a basic understanding of how telephone wiring works is useful before attempting to make such a switch.” Link.
HOW TO – Distribute VoIP throughout your home