Mathematics Games & Problem Solving

Math Games
Sports Math Mania -- Baseball and Basketball problems to solve created by our own 4th graders.
Math Playground -- an action packed site for students in grades K to 6. 
Practice your math skills, play a logic game and have some fun!
Aplusmath--There are games, flashcards, puzzles, and so much more
CartoonMath--a complete set of online multiplication flashcards, developed for students having difficulty memorizing the multiplication tables, using fun picture and rhyme associations
Clever Games for Clever People--Math games to help students understand various concepts
Change Maker Game--Change Maker Game to teach money skills
Edbydesign.com--kids can play scrambler puzzles, maths games and publish stories, jokes and poems online.  Practical ideas for parents, teachers on language, math and special needs
Lemonade Stand--Math simulation game for kids
Math Baseball--Play Math Baseball!
ProblemSolving - site by kids as an entry for ThinkQuest
Save the Solar System--and learn Multiplication at the same time.  As the pilot of a space ship far in the future, you must save the solar system from gravitational anomalies while learning and memorizing the multiplication table. This is a game Dan Perkins developed for his son to help him learn his tables.

Puzzles and Problem Solving
AIMS' Puzzle-a-month page
Figure this--Math Challenges for families
FunBrain.com--providing teachers, parents, and kids with the tools they need to succeed
Houghton-Mifflin Brain Teasers--fun brain teasers by grade level
Weekly Brain Booster
Interactive Math Puzzles
The International Mathematics Olympiad--an annual mathematics competition
MathForum Problem of the Week - new problems each week - good variety
Cool Math For Kids - amusement park format - appealing and fun!