Desmos - Free graphing calculator.
Khan Academy - Videos and other resources to help you learn new math concepts or refresh your memory on old ones.
Math Games Algebra Calculus - Games to help learn math concepts.
MathTV.com - Short videos on study skills, basic math, algebra, geometry, trigonometry, and calculus.
Mathematical Imagery - Works of art made by using math.
Mathematics - From Saylor.org, various free courses on math, including courses that will help students transition between high school and college level math.
Mathematical Fiction - Find books to read that feature mathematics.
Paul's Online Math Notes - Free and downloadable math notes and tutorials.
Purple Math - Algebra help
Wolfram Alpha - Math examples