Most cell phone companies offer pre-paid wireless which is a much better option for people with bad or no credit.
You have to figure out about how many minutes of usage you need per month, then compare the companies and rates to see which one comes out best for you. http://www.cellguru.net/prepaid_compare.htm has a nice chart.
For me, Tracfone is not a good value, but I know some people who swear by it, but they only buy minutes when they are on sale and using various coupon codes online.