Cut The Knot- a plethera of mathematical resources and games to help with algebra, geometry, arithmetic, probability, and much more.
Geometry of the Ancients - An exploration into area, perimeter, and volume. Topics include:- Basic Skills, Concepts, Critical Thinking Problems and Applications, Rectangles, Triangles, Trapezoids, Circles and more.
Math Goodies - your free math portal featuring interactive lessons, worksheets, and homework help.
MathOps - Free and subscription online prealgebra and algebra course. It is like having your own private math teather or tutor, but with interactive lessons you access whenever you are ready.
Purplemath- Algebra lessons are written with the student in mind. These lessons emphasize the practicalities rather than the technacalities, demonstrating dependable techniques, warning of likely "trick" questions, and pointing out common mistakes.
Taxicab Treasure Hunt - On the surface, this activity is a simple game that gives students practice with coordinates. But it is also intended as an introduction to taxicab geometry, which is a gateway to non-Euclidean geometry. That is, in everyday geometry, the shortest distance between two points is a straight line, but in Taxicab geometry, a straight line is not always possible.
Problem Solving
Alive Maths- attractive and engaging environment motivating and encouraging students to mathemitize. Suited to exploration, manipulation, and representation.
The Chaos Game - improve students' geometric intuition and algorithmic thinking.
Khan Academy - Watch. Practice. Learn almost anything - for free. Over 2,100 videos and 100 self-paced exercises and assessments covering everything from arithmetic, physics, finance, and calculus.
Math Is Fun - combining fun and mathematics to help improve basic math skills.