Practice Your Math Facts:
Math Playground - a site for elementary and middle school students to practice math, play logic games, solve word problems and more. This site does contain ads.
http://MathPlayground.com/index.html
Math Live - 3rd - 6th graders may watch animated cartoons to learn math concepts.
http://www.learnalberta.ca/content/me5l/html/math5.html#
Math Magician - Are you a math magician? Test your skill and earn a certificate.
http://www.classbrain.com/artgames/publish/math_magician_games.shtml
Fact Dash - practice math facts fast
http://www.mhschool.com/math/2003/student/factdash/popup.html
That's a Fact! -
Set your own pace to check your knowledge of addition, subtraction, multiplication, and division facts and to improve your memorization skills.
http://www.harcourtschool.com/activity/thats_a_fact/english_K_3.html
Arcademic Skill Builders - Practice your math facts with arcade style games against the computer or other students.
http://www.arcademicskillbuilders.com/
Stop the Clock Match the time to the clock as fast as you can!
http://www.oswego.org/ocsd-web/games/StopTheClock/sthec3.html
Flips, Slides and Turns
http://www.harcourtschool.com/activity/icy_slides_flips_turns/
Oswego City School District (NY) Educational Math Games
http://resources.oswego.org/games/
Math Activities from Harcourt School Publishers
http://www.harcourtschool.com/menus/preview/harcourt_math/activities04.html
National Library of Virtual Manipulatives