I wanted to have a phone for my upcoming trip. I didn't want to pay $30+ a month for a regular contract phone, so I got a TracFone. The phone (I got the cheap one) was $30, including 10 minutes of airtime, and 100 minutes was $25 (plus tax even though I bought it on-line, assholes), and for filling out a survey when I activated the phone I got a bonus that I would get 40 free minutes every time I bought 100 or more minutes as long as I keep the phone activated. I also got 10 extra minutes for activating the phone on the web instead of by phone. So I got a teeny little phone that seems to work and 160 minutes, good until November, for less than my mom pays for two months on her (pretty cheap) regular billed cell phone.
Even though the prepaid cell phones seem to be targeted at the demographic of people who won't pass the credit check for a regular phone contract, the TracFone appears to be a very good deal for the person who wants to have a phone available but doesn't actually plan to use it very much. The minimum cost to keep the account active is $20 (plus sales tax) every 60 days -- call it $11 a month. This beats the pants off of any billed plan I've ever heard of. I'll try to remember to report back in a few months about how well it works technically and whether it still seems like a good idea economically.
I didn't mean this to be an advertisement for TracFone, but if this makes you want to run out and buy one, email me at my LJ address and I can send you an "invite"; if you use it I get a bonus of like $40 worth of airtime. I dunno if you get a bonus for using the referral rather than just signing up, but if you don't and did it anyway, I'd owe you a beer or something.