Cingular (AT&T) has a 10$ phone pay as you go plan that looks like what your looking for.

When getting prepaid plans, check the expiration of the minutes. For many, if you don't keep loading minutes onto it, they can expire. If you load $100 onto the T-Mobile prepaid, they don't expire for a year. Combine that with a $49 phone and you've got a decent setup. Not really cheap up front but at least it will last you a year before you need to add more minutes. http://www.t-mobile.com