Calculus Derivatives and Limits Reference Sheet (1 page PDF)

Algebra Quick Reference - PDF

Electrical Engineering Community's Tools - geometry reference sheet - many more on this site

Trigonometry Laws and Identities Math Reference Sheet (1 page PDF)

Animated trigonometry

Not in English, but still lovely lovely math.

Fast Algebra Techniques

Math is not everyone’s cup of tea, but learning new math shortcuts can be a lot of fun. There are many of them to learn. This infographic happens to cover 6 math shortcuts: [via: Center of Math]

Geometry Right Triangles and Trigonometry Quick Reference Sheets