ProFootball API is an API dedicated to delivering live NFL stats. It was built to serve the needs of programmers who wanted access programmatically to the stats while games are being played, without breaking the bank.
In addition to live stats, ProFootball API also offers access to stats from the last five years. It is great for simple queries, but can also return data sets large enough to answer whatever questions you might have.
To get started, create an account and grab your API key. Then head over to the authentication page to start making requests.