An amazing tool for learning at your own pace, reviewing a lesson you learned in class that morning, or for step-by-step problem solving, Khan Academy offers video lessons and practice problems for a very broad range of topics (and not just for math!)
This is an amazing website to start with!
Udacity offers free, video-based courses to teach a variety of technology-related topics. Make sure you search for "free" on the sidebar.
Wolfram Math World
An extensive math resource that offers definitions and examples.
Just Math Tutorials
Math videos on virtually any topic.
MIT Course Materials- online, for free!
Open Source Textbook Library
University of Minnesota compiled a open source textbook library whose Math sections covers topics such as statistics, calculus, multivariable calculus, linear algebra, and real analysis.
Interested in web design, programming, or data science? Codecademy is an amazing, interactive, and free website which guides you through learning different topics in coding and different languages as well!
Statistics 101 (YouTube)
This channel on YouTube offers statistics help with a vast scope of topics.
Crash Course- Statistics
A YouTube Playlist from the Channel "CrashCouse". Learn about the big picture of concepts in statistics and how they apply to your work.
MIT Calculus for Beginners
Although this page introduces calculus for "beginners and artists", this is a great resource for anyone who likes to learn through reading and who would like to begin to understand what calculus is about.
Topology without Tears, Sidney A. Morris
Topology is the study of abstract spaces, their properties, and the maps between them that preserve these properties. It is colloquially known as rubber sheet geometry and can be thought of as doing geometry without a notion of position, length, or distance. Topology without Tears by Sidney A Morris is a fantastic introduction to Topology. It covers Topological Spaces, Continuity, Compactness, Connectedness, Metric Spaces, Quotient Spaces, and more. It also has appendices on Topological Groups and Chaos Theory.
Abstract Algebra is the study of sets that have an operation that behave a lot like multiplication. It is often used to classify the symmetries of crystalline structures or to develop complex cryptographical systems. Abstract Algebra: Theory and Applications by Tom Judson is an open source Algebra course that covers the scope of a standard one semester undergraduate course and more. This textbook has a breadth of proof and computation exercises as well as SAGE exercises. A great text to learn SAGE.
An incredibly thorough (<1000 pages) introduction to Chaos Theory. Chaos is a fascinating and complex subject that is very difficult to introduce while assuming minimal prior knowledge. Chaos Book is geared towards teaching physicists and therefore covers the important concepts such as Flows, Lyapunov Exponents, Hamiltonians, Turbulence, etc with an eye towards simplicity. A rewarding text that provides ample exercises and great references to other texts (many of which are in our library!)