Recently arxiv.org added a Code Tab towards the end of paper descriptions. Which contains links to both the official and community code.
I don't know if this is the case for all the papers or not till know. But I'm sure it'll be extended to all the papers in a short while.
Another good (although a bit old) and freely available online book (apart from the one suggested in this answer) is Neural Networks - A Systematic Introduction (1996) by Raul Rojas. This book contains several exercises at the end of each chapter and covers topics that you will not find in many online courses.