Harcourt Math
http://www.harcourtschool.com
Interactive practice by grade level and topic using our current adopted math curriculum for grades Kindergarten through Fifth.

Harcourt Multimedia Math Glossary 
http://www.hbschool.com/glossary/math/
Interactive, animated math glossary for Grades 1-8.
 
AAA Math
http://www.aaamath.com
Interactive practice and estimation games sorted by grade level and math topic.  Grades K-8
 
Visual Fractions
http://www.visualfractions.com/
Interactive practice to help students visualize fractions.  Grades 3-8
 
Cool Math 4 Kids
http://www.coolmath4kids.com Grades K-5
http://www.coolmath4kids.com/mathgames/ Grades 3-8
Interactive math activities for students with games, calculators, etc.
 
Create A Graph
http://nces.ed.gov/nceskids/graphing
Create bar, line, area, or pie graphs online!  You submit the data and the website does the rest!  Grades 2-8
 
K-8 Online Animated Interactive Lessons
http://www.dositey.com/index.html
Free animated online workbooks for the development of reading and math skills, Grades K-8. You can also print out free worksheets.
 
Interactive Math
http://matti.usu.edu/nlvm2/nav/index.html
Series of math activities designed for Grades K-12
 
Escape From Knab
http://www.escapefromknab.com
Escape From Knab was created by the financial institution Firstar to help students develop financial strategies that will enable them to make sound decisions about day to day financial matters. (Shockwave required.)
Grades 6-8
 
Get Smarter
http://www.getsmarter.org/
Get Smarter is an interactive site where students can compare their math and science achievement against others worldwide.  Grades 3-12
 
Math Flash Cards
http://www.edu4kids.com/math
Math flash cards provides easy to complex problems utilizing addition, subtraction, multiplication, and division.  Grades 1-12
 
AAA Math
http://www.aaamath.com
While the pages offered are limited in 3 of the 4 areas (science, math, language arts and social studies) this is still a resource worth using.
Grades Pre-K-12
 
Grade 7 Math Interactive Lessons
http://www.zone101.com/LearningZone/MathZones/mexer7.htm
Mathzone's online math lessons for Grade 7
 
ExploreMath.com
http://www.exploremath.com/activities/activity_list.cfm?categoryID=14
Explore Math offers a variety of resources to teach mathematics, including multimedia learning activities that enable teachers to illustrate difficult math concepts with interactive simulations.  Try Explore Math Gizmos Grades 6-12
 
Free Puzzles.com
http://www.freepuzzles.com/puzzles/PuzzlePage.asp?PuzzleNumber=Math012&CategoryID=3
Free Puzzles offers interactive math and geometry puzzles with solutions.  Grades 3-12
 
Kids Math
http://www.kidsmath.com/e_int.html
Math activities for grades 1-5
 
Kids Math Pre-Algebra
http://www.kidsmath.com/Algebra.html
Online quiz based on pre-algrebra skills  Grades 6-8
 
Interactive Algebra
http://www.fifeschools.com/math/algebra/Algebra.html
Interactive practice page with lessons on equations, factoring, and graphing. Requires JavaScript and Java. Grades 6+
 
Interactive Math
http://www.cut-the-knot.org/Curriculum/index.shtml
A variety of math activites that include arithmetic, geometry, algebra, calculus  fractals, and probability.  Grades 2-12
 
Zona Land: Graphing X-Y Scaling
http://id.mind.net/~zona/mmts/graphPaper/scalingGraphPaper/scalingGraphPaper.html
Interactive web page for demonstrating the interaction of the X and Y axis on graphs.  Grades 6-12
 
Calculator's On-line Center
http://www-sci.lib.uci.edu/HSG/RefCalculators.html
Links to more than 9600 interactive Web calculators, covering applications to many fields.  Grades 3+
 
Interactive Math Site
http://www.c3.lanl.gov/mega-math/index.html
Games teaching color theory, knots, algorithms, graphs and more.  Grades 6+
 
Illuminations
http://illuminations.nctm.org/imath
This is a must see for every math teacher. Each grade level section includes lesson plans, interactive lessons for students and an interactive version of NCTM Standards. Be sure to bookmark this one!
Grades Pre-k-12
 
Interactive Mathematics Miscellany and Puzzles
http://www.cut-the-knot.com/Curriculum/index.shtml
Math site with puzzles, games, a math glossary, and more.  All Grades
 
Math Goodies: Interactive Math Lessons With A Problem-Solving Approach!
http://www.mathgoodies.com/
A free educational site featuring interactive math lessons.  All Grades

QuickMath
http://quickmath.com
QuickMath is an online calculator that solves equations and does all sorts of algebra and calculus problems - instantly and automatically! The answer is then displayed on your browser, usually within a couple of seconds.  Grades 9-12

The Math Forum @ Drexel's Ask Dr. Math
http://www.mathforum.org/dr.math
The Math Forum @ Drexel's Ask Dr. Math is a database of math problems with tutorial solutions that lets students search for problems similar to those on their homework.  All Grades

Math Glossary
http://www.hbschool.com/glossary/math
Math Glossary provides illustrated and animated definitions and explanations for math terms to help students with homework.  Grades K-6

SchoolHouse Rock
http://www.apocalypse.org/pub/u/gilly/Schoolhouse_Rock/HTML/schoolhouse.html
This site has lots of catchy tunes here help students learn about grammar, America, mathematics, science, and computers. The RealPlayer plug-in is required for the audio and video files. Grades 2-5

The Counting Story
http://www.magickeys.com/books/count/index.html
This site is illustrated with animated pink bunnies that do different tricks on each number page.  Grades PreK-1

Fun Brain
http://www.funbrain.com/cgi-bin/getskill.cgi?A4=1
This site contains a variety of edu-taining activities covering areas of math, language arts, social studies, and science.  Grades K-6
 
Teach R Kids Math
http://www.teachrkids.com/
Students learn number basics, addition, subtraction, fractions, and much more with interactive online math worksheets. Grades PreK-3
 
BasketMath Interactive
http://www.scienceacademy.com/BI/index.html
Students choose a math skill from the table of contents and a mathematics question and animation based on a basketball game appears.  Click the Results option to get a score.
 
Silver Burdett Gin Math Activites
http://www.sbgmath.com/act.html
Ready to use math activity descriptions, activity sheets and answer keys.  Grades 3-6
 
Go Math
http://www.gomath.com
Online math with 3-D Virtual Physics, Algebra and Geometry Solutions, graphs (AutoGraph) SAT Math, and interactive tutorials and quizzes.  Note:  Some areas are not available to the general public.  Grades 6-12
 
King's List of Online Math Activities
http://www.k111.k12.il.us/king/math.htm
A huge listing of math interactive activities for all grades. Grades K-12

Math Exercises
http://www.syvum.com/math/arithmetic/level1.html
Online activites for levels 1-4.  Watch for watch pop-ups, expecially Gator!

Math Advantage (Harcourt Brace)
http://www.harcourtschool.com/menus/math_advantage.html
Online resource for grades K-12.  Note:  Grade 1 does not work.

Interactive Math Activities
http://www.globalclassroom.org/authors/florida/math/interactive.html
Pattern Blocks, base ten, and integer activities.  Grades K-2
 
Primary Grades Interactive Math Site

http://www.globalclassroom.org/ecell00/javamath.html
Huge listing of sites related to specific math skills.  Grades K-3
 
Measure 4 Measure
http://www.wolinskyweb.net/measure.htm#science
A complete list of online calculators and converters.  Grades 3-12