I have cable internet and Packet8 VOIP. I will never go back to landline. With Packet8 I get unlimited calls to the US and Canada for $19.95 a month. Worldwide, the calls are less than $0.10 a minute. There are no hidden fees. I get free voicemail, call forwarding, voicemail, etc. It works with a regular phone and you can make and receive calls to and from any number (cell or landline) in the world. You also have the option to choose a number anywhere in the Packet8 network. If you have a lot of relatives or business contacts in one particular area of the country, you could choose a number local to them and it would not be a toll call for them to reach you. You can also take your phone adapter with you anywhere in the world with a broadband connection and still place and receive calls as if you were sitting in your living room. I've had absolutely no interruptions in the 2 months that I've had service.
http://www.packet8.net