Pure TalkUSA, an MVNO reselling AT&T service. Called the Unlimited Plus plan it includes unlimited voice minutes and SMS text messages plus 100 MB of data and 100 MMS picture messages for $43.95 a month.
There is a small gotcha with this plan. You are required to register a credit or debit card with PureTalkUSA in enroll in this plan. If you use up either the 100 MB of data or the 100 picture messages in a month you will automatically be charged an additional $10 and your data and MMS counters will be be reset giving you a fresh allotment of 100 MB and 100 MMS. If you are using a smartphone you can burn through 100 MB pretty quickly and easily rack up a sizable bill. A more consumer friendly approach would be an option for customers to disable automatic overage billing.