Fact Monster is a free reference site for students, teachers, and parents. Get homework help and find facts on thousands of subjects, including sports, entertainment, geography, history, biography, education, and health.
Cool Math has free online cool math lessons, cool math games and fun math activities. Really clear math lessons (pre-algebra, algebra, precalculus), cool math games, online graphing calculators, geometry art, fractals, polyhedra, parents and teachers areas too.
Action packed math site for elementary and middle school students featuring math games, math word problems, math worksheets, logic puzzles, and math videos.
Mr. Hui's XP Math features free math games aligned to Common Core State Standards: Number Sense and Operations, Algebra, Geometry, Measurement, and Data Analysis and Probability.