Your should checkout the Vonange web site they explain how it works and have some demos. To go from analog requires something like Cisco's ATA which converts the anlog signal to digital for use over IP. I have been running Vonage for three or four years now without any trouble and it's cheap 24.95 a month unlimited calls. Anyway they have FAQ section that may help you a bit. VOIP still has a ways to go but day by day it's becoming beter. Most the time my vonage or VOIP phone works beter than ma bells.
I'd like to learn more about VOIP. Is there any articles to recommend for reading? And is application like Skype, PC Telephone also considered as VOIP?
And I came across an advertisement of D-Link DVG-G1402S wireless router with embedded VOIP functionality. Does this router provide the same functionality of a traditional router (that is to provide Internet connection to the PC) and at the same time, you can connect a analogue phone and fax machine to it if a VOIP service is engaged?