VoIP has two BIG things going for it: It's flexible and cheap.
You can call from wherever you can get a broadband connection. You just need an adapter (ATA), or an IP phone or a computer. And, of course, an Internet service provider, but who doesn't have one of those these days.
Since IP phones or ATAs send their info over the Internet, they can be managed by the provider wherever there's a connection. VoIP is a boon to business travelers who can pack their phones or ATAs on trips and always have access to their home phones.
A VoIP phone plan can cost you as little as $30 a month. You'd have a minute-rate plan similar to a cell phone bill. Some VoIP companies offer unlimited plans for around $79. These higher-end plans offer a set of free features including caller ID and call waiting for which the regular phone company charges extra.