Add 'Em Up - (primarygames.com) - add two numbers and click on correct answer
Addition Concentration - (aplusmath.com) - two-digit addition - fun (needs JAVA)
Addition Flashcards - (aplusmath.com) - great easy math
Addition Hidden Picture - (aplusmath.com) - fun math (needs JAVA)
Addition Matho - (aplusmath.com) - fun game - two-digit addition (needs JAVA)
Addition Mystery Game - (dositey.com) - great
Addition Surprise! - (harcourtschool.com)
Addition Tunnel Blaster - (playkidsgames.com) - Make sure to read the instructions - keep on your toes for this activity
Spacey Math - (learningplanet.com) - addition, subtraction, multiplication and division games - fun
The Number Monster - (coolmath4kids.com) - addition, subtraction, multiplication, division - levels from easy to killer - good
Two Minute Warning - (primarygames.com) - two minutes to do fairly simple math (0-19) (add, subtract, multiplication, and division)

Count Us In - Games to help students understand basic number concepts

Decimal and Fraction matching - (oswego.org)

Division Facts - (quia.com) - 2 game choices - good
Spacey Math - (learningplanet.com) - addition, subtraction, multiplication and division games - fun
The Number Monster - (coolmath4kids.com) - addition, subtraction, multiplication, division - levels from easy to killer - good
Two Minute Warning - (primarygames.com) - two minutes to do fairly simple math (0-19) (add, subtract, multiplication, and division)

Decimal and Fraction matching - (oswego.org)
Equivalent Fractions - (quia.com) - 3 game choices - good
Fresh Baked Fractions - FunBrain
Who Wants Pizza? - (math.rice.edu) - activity about Fractions - fun and simple

Geometric Terms - (quia.com) - 4 games choices - good for upper grades

Billy Bug - (oswego.org) - grid interactive game

Customary Measurement - (quia.com) - 3 game choices - good for upper grades

Change Maker - FunBrain
Counting Change - (quia.com) - 3 game choices - good

Multiplication Facts Review - (quia.com) - 3 game choices - good
Multiplication Mystery - (harcourtschool.com) - like "Addition Surprise" only it's multiplication
Spacey Math - (learningplanet.com) - addition, subtraction, multiplication and division games - fun
The Number Monster - (coolmath4kids.com) - addition, subtraction, multiplication, division - levels from easy to killer - good
Two Minute Warning - (primarygames.com) - two minutes to do fairly simple math (0-19) (add, subtract, multiplication, and division)

Ordering : Least to Greatest - (oswego.org)

Pattern Blocks and Manipulatives - (arcytech.org) - online activity

AAA Math - 3rd Grade - (aaamath.com) - click on Place Values (there are several) - games are below instructions
Place Value Game - (funbrain.com) - Funbrain
Place Value Placer - FunBrain

Spacey Math - (learningplanet.com) - addition, subtraction, multiplication and division games - fun
Subtraction Tunnel Blaster - (playkidsgames.com) - includes negative numbers
Take it Away - (primarygames.com - subtract two numbers and click on correct answer
The Number Monster - (coolmath4kids.com) - addition, subtraction, multiplication, division - levels from easy to killer - good
Two Minute Warning - (primarygames.com) - two minutes to do fairly simple math (0-19) (add, subtract, multiplication, and division)

Willy the Watchdog - (harcourtschool.com) - telling time
Tick Tock... on the Office Clock - great links to worksheets and games for Telling Time skills

Easy Roman Numerals - (quia.com) - 4 game choices -- good
Fifth Grade Math - (aaamath.com) - excellent site
FunBrain - lots of games (Math)

One False Move
Math Baseball - two players
Change Maker
Fresh Baked Fractions
Cookie Dough
Place Value Placer
Tic Tac Toe Squares

Harcourt Math Activities - (need Shockwave) - free preview activities from the textbook website
Internet4classrooms -- great site - scroll down to the bottom for various grades --Assessment category
Leap for Fun - interactive board game for 1-4 players (needs Shockwave)

Learning Planet - several online math games (Math Mayhem, Fraction Frenzy, Spacey Math)
Math links - (dositey.com) - click on the appropriate grade level
Math Online - (mhschool.com) - preview activities from the textbook by grade
Mathematics Index - (kidport.com) - click on the appropriate problems - easy to harder
Riley's Monster Crunch - (kidscom.com) - like a computer game program - really good
Room 108 Math - (netrover.com) - great links to some fun games
The Little Animals Activity Center - (bbc.co.uk) - cute site with activities including math and reading

Dositey.com - free interactive lessons, exercises and worksheets, educational games, open-ended questions in Math and Language Arts by grades (explore which games are ready to use before hand)
Math Online - (mhschool.com) - textbook activities - choose grade

Interactive Examples of NCTM Standards - (standards.nctm.org) - good for all grades - patterns and grids