It could depend on which programming language one is using. For eg: I use python and I love sentdex. But it could be different depending upon your language of choice.
Without a doubt python. I have been doing Machine Learning and Neural Network Programming for over a year now. Availability of good libraries such as scikit-learn and tensorflow along with the easiness of python makes python the go-to language for AI programming in my opinion.
Python is one of the fastest growing programming languages today. The main advantage I see in learning python is its ease of code. Also, minimal setup compared to other programming languages such as C# and Java makes python a popular choice for beginner programmers.
Other than that, you can do many amazing things using python. From desktop application development, web development, game development to complex tasks like Machine Learning, data science, computer vision etc. can be easily done in python. There are many new types of research going on in the field of self-driving cars, image recognition, smart recommendation feeds, Natural Language processing etc. using python which means if you learn python, you'll be able to land yourself in programming industry easily.
I am a research programmer myself and I am currently working on the site http://www.python36.com/ to make quality tutorials of python available for free. I have just started and it's still in the beginning phase but keep updated so that you can learn more from there. Cheers!!!
https://www.youtube.com/user/sentdex