Tracfone, they have some nice ones that are contract or pay as you go, and all are dirt cheap. I get the phones loaded w/ 1 yr service and 1500 minutes talk time for $60. You can add air time, or just internet time. They use the Sprint network I think?
Here's the ultimate cheap phone idea.....there's apps you can download to your old, not in service phone that allow you to make calls using the internet (which any of these dead phones can still access). Some are totally free, some have a small price for the app. What a great idea.