I looked at Vonage, and figured why pay them? There is free software for talking to other users, and they have minimal charges to make it work with regular phones. I use Gizmo, but Skype is very popular. Check 'em out and see what you think. I got an mvox, nice little speakerphone with great sound quality ($39, I think). I have a phone number with my US area code so Mom and friends can call us at no extra cost to them (or me). So far this is definitely cheaper than the Vonage cheap plan, and cheaper than my landline was in the states.
I have found one issue here: I can call a Belize landline with Gizmo (~.24 a minute I think), but I can't call the Belize mobile phones. My friend started Gizmo (that might be why I use it :-), and he told me he'd get that fixed. My wild guess is that it's a billing problem, because here, the calling party pays for the call, the mobile user does not. I have no idea if Skype would work to call Belize mobiles, not sure if I want to install it.