Word on the street (via engadget) is that Verizon will be offering unlimited calling, data and messaging packages in the very, very near future (as early as 2/19/08).
Engadget is reporting the packages might look like this:

$100 – Nationwide Unlimited (voice)
$120 – Nationwide Select Unlimited (voice, SMS, MMS)
$140 – Nationwide Premium (voice, SMS, MMS, VZNav, VCAST, [...]