You can also get a plain old bring-your-own-phone pay by the month plan from T-Mobile for $30/month that gives you 100 minutes of voice, unlimited texts, and sorta-unlimited data (1st 5GB at 4G and then it degrades)
It's the one with this disclaimer: "New activations only. Available exclusively in-store at Walmart, on Walmart.com, and T-Mobile.com."
They also released this $200 phone to go along with the plan: http://www.engadget.com/2011/10/26/samsung-exhibit-ii-4g-to-...