phone plans

Depends on the carrier. You can get a Samsung Precedent (it's on Sprint through Straight Talk) for about $50. The Huawei Ascend Y (reconditioned) and the LG Optimus Q are also $50.You get 2.5GB/month for $45.

Don't expect too much from phones in that price range, though. If all you want is tethering, and don't mind 3G speed, they'll work.

(There are other ways to go - cheap phones on Virgin or other MVNOs, but all about the same price. Once an Android phone drops below $50 new, you usually don't see it any more.)