With the growth of machine learning, many people are looking into libraries and tutorials on learning more about machine learning.
TensorFlow is no exception, originally developed by engineers of Googles Brain Team, is an excellent python library providing necessary operations to do numerical computation using data flow graphs. TensorFlow was open sourced a year ago by Google, who has used it internally for their machine learning and deep neural network learning. TensorFlow is written is C++ and is highly optimized for deploying computation onto multiple CPUs and GPUs. On GitHub TensorFlow has a 600 member contributor team, with over 12,000 commits making it one of the more popular projects listed on GitHub.
If you are interested in learning more about TensorFlow, you can visit their main website at : https://www.tensorflow.org
If you want to contribute and look at the source code, you can find more information on the official TensorFlow GitHub page at : https://github.com/tensorflow/tensorflow
For more hands on tutorials and starter here are some good starting places : Official TensorFlow Getting Started : https://www.tensorflow.org/get_started/
Website dedicated to Teaching TensorFlow : http://learningtensorflow.com/