I'm using an old Nokia 5185i as a "glovebox phone" with PP, cost $15 to activate with 100 minutes (get PP activation off ebay)
There is a $0.50/month fee (you lose a few minutes/month), so the
effective rate for the cheapest refill works out to about 18 cents/minute
Since this is an occasional use phone, I like the 120 days before minutes expire that PP offers (90 days max for most others) - but, for the activation kit only, minutes expire in 90 days instead of the normal 120 days
Roaming is too expensive ($2/minute!) for even occasional use, so get something else if Verizon has poor coverage in your area.
Here in the Carolinas, the other cheap prepaid for occasional users would be STI Mobile (but you pay close to $100 up front, and wait for a rebate) or CPS (Verizon as well, but more expensive per minute than PP)