MathGrade.com

Math Number Puzzles
200 Math Number Puzzles, including arithmetic, rounding, fractions, decimals, algebra, multiplication, ratios, word problems, and order of operations.
www.edhelper.com/

Ben Robinson's Cross-Number Puzzles
A collection of cross-number puzzles: similar to crosswords, but using digits instead of letters. Many involve complex mathematical reasoning.
www.users.bigpond.com/

Nick's Mathematical Puzzles
A collection of an assortment of problems to try to solve, with hints, and solutions. Includes daily update feed link.
www.qbyte.org/

Brain Teasers and Math Puzzles
Interactive puzzles to challenge logic and mathematical skills. Immediate feedback with detailed solutions is provided.
www.syvum.com/

Home Page of J. S. Milne
Includes preprints and course notes on Group Theory, Fields and Galois Theory, Algebraic Geometry, Algebraic Number Theory,Modular Functions and Modular Forms, Elliptic Curves, Abelian Varieties, Etale Cohomology, and Class Field Theory.
www.jmilne.org/

Algebraic Math Puzzles
A collection of puzzles at high school level. Does not include answers.
www.lifesmith.com/

Silverman, Joseph
Mathematician at Brown University, with links to publications and courses.
www.math.brown.edu/

Math Forum
Resources, problems and forum for teachers and students in mathematics.
mathforum.org/

Alphametics Page
Explains this combination of arithmetic and words, and provides examples of several different types.
members.aol.com/

Math Puzzles
Logic puzzles and riddles with some solutions.
www.math.utah.edu/