If you're looking to run a successful developer program, you should probably pay attention to Mathys van Abbe. He's the founder of Mobypicture (our Mobypicture API profile), which has just celebrated its 500th developer.
Streamzoo, an alternative to Instagram, has just released the Streamzoo API. According to the documentation, the API uses HTTP calls and returns JSON. It joins 341 photo APIs in the ProgrammableWeb directory.