Its definitely a subset of AI, but if you are interested in Machine Learning then you should check out the Deep Learning Tutorials [deeplearning.net]. They cover most of the building blocks of "Deep Learning", which you can think of as the new wave of Artificial Neural Networks. The tutorials include complete theoretical (and mathematical) descriptions of the model, as well as Python/Theano implementations. Pre-requisites would be a good math background (first year calculus should suffice), basic probability theory and coding in Python/numpy. You can learn Theano as you go along.
ps: sorry for the repost, forgot to log-in beforehand.