Ask HN: Recommended resources for learning stats for machine learning?

I have fair understanding of Python, Numpy and Pandas. Recently I started learning Scikit-learn and I realize I know next to nothing about statistics and for this reason I am finding it difficult to get a clear mental model of what some particular classifier is doing and what are it's pros and cons.

For this reason, I am looking for some introductory materials related to statistics (preferably online reading/pdf) which may help me start relatively easy. It would be great if the materials is written with the perspective of machine learning.

Any recommendations?