IBM's API: https://github.com/IBM/qiskit-sdk-py
Rigetti Computing's Forest: http://forest.rigetti.com/ https://github.com/rigetticomputing/pyquil
ProjectQ: http://projectq.ch/
We added a really basic introduction to quantum programming into Forest that you might enjoy: http://pyquil.readthedocs.io/en/latest/intro_to_qc.html