We are fulltiming and use highstream (
www.highstream.net). We pay $8.99/month and they have numbers all over. They have some of their own numbers but also lease from earthlink, aol, and maybe others. We've only had two or three places with no local number in 21 months of fulltiming. But in those locations nobody had numbers. I've never had a busy signal. Usage is unlimited from what I can tell. They do not provide free webspace. You can set up your system to use the windows dialer or you can download and install their dialer. I use both but usually use theirs because it has all the numbers right in the dialer. I just click on the state and city and it shows me all the numbers. I click one and tell it to dial. You will need to ask the rv park if you need to dial 9. Some places you also dial the area code, too. So ask. We've been very happy with highstream. Let me know if there are any questions about them I can answer for you. You sign up online and are active within seconds. When I signed up there was a $5 one-time fee for setup. I don't know what it is now.
Also, if your system doesn't have builtin wi-fi you might consider buying a card or usb wi-fi connector. More and more parks are providing wi-fi, which is at least as fast as cable/road runner. I'm on wi-fi right now. Some parks provide/loan/sell wi-fi cards if you don't have one. Some parks provide free wi-fi but most you have to sign up and pay for. Usually the monthly rates are reasonable. Sometimes weekly and/or daily rates are reasonable. Sometimes they're ridiculous and we go back to using dialup. The one I'm on now is $29.99/month but their daily rate is ridiculous. Don't remember their weekly rate.
We got a cheap calling card from Sam's, something like $40 for 1250 minutes or thereabouts. In those few places where we had no highstream number we used the calling card to call long distance but did only email that way.