My family is down with a cold, so I'll make this quick.
Thank you for all the prepaid cell phone comments! Our T-Mobile Family Plan contract runs out this month, and we're really not getting our money's worth. At least on my end--I use the phone so rarely it loses charge before I need it again. In fact, my reaction to thoughtless cell-phone shoppers and drivers is to retreat even farther from new millenium technology. My husband teases me about this attitude, to which I reply, "Hey, at least I have a BLOG...so who's behind on the times, now?"
A summary of your helpful advice:
If you rarely use a cell phone, prepaid service is the cheapest option.
A big expense of the prepaid system is the phone itself, but you can buy them used online.
You can save money on minutes by buying at Sam's Club or bidding for minutes on Ebay.
Don't wait until you are low on minutes to bid for more airtime on Ebay.
When you win an auction for minutes, you send the seller your esn#, and the seller will email you the codes to enter. (Dena)
Tracfone is probably the largest and most reputable prepaid company (Kathryn).
Virgin Mobile offers frequent deals, rolls minutes over, and gives you a grace period if you forget to renew your minutes quarterly. (Coffee and a Muffin).