First, if you are starting with mathematics, begin with the Khan Academy lectures.

These are fantastic resources for the future as well. If you are stuck at any stage, chances are Khan Academy will help you.

If you are comfortable with high school mathematics and want to go deeper, check out this course by @TreforBazett.

It's humbly titled Discrete Math, but it's much more than that. It's a fantastic introduction to mathematics and mathematical thinking.

1. Linear algebra

First encounter with linear algebra? Start with "Introduction to Linear Algebra" course by Gilbert Strang, taught at MIT.

Once you master the basics, the following course will help you reach the pinnacle of linear algebra.

It's titled "Matrix Methods in Data Analysis, Signal Processing, and Machine Learning", again taught by the great Gilbert Strang.

2. Calculus

To master differentiation and integration, start with the "Single Variable Calculus" course at MIT.

The next step is multivariable calculus.

Single-variable calculus introduces the ideas. Multivariable calculus builds the tools we use every day.

This course is taught by Denis Auroux at MIT.

The fundamentals are clearly and concisely covered by the "Probabilistic Systems Analysis and Applied Probability" course by John Tsitsiklis, once more from MIT.

(I know, that's a lot of courses from MIT. This is not an accident.)

Want to understand the principles of making decisions from data? Check out "Statistics for Applications", taught by Philippe Rigollet.