If you don't want to play the "family plan" game, then you probably want to have a serious look at Walmart's "Straight Talk" plan, or the T-Mobile pre-paid plans that you can only get online. Perhaps the cheapest option around is Republic Wireless. You have to use their specific Android phone, which is something of a bummer, but they get you a low price ($20/mo) by routing calls over WiFi as much as they can, then falling back to Sprint if that's not available.