Who has the best deals?

I currently have a prepaid cellphone which works fine for emergencies but isn't that great for everyday use. I'm wondering what else is out there that I should be looking at instead. Also, would a credit check, etc be required for a monthly plan somewhere? Is it better through an individual company (for example T-Mobile or Verizon at the local mall) as opposed to say buying a phone and setting up a monthly plan through any of those companies at the local Walmart electronics dept which also offers that option?