Grade 4 Math

Algebraic Thinking
Algebra Meltdown
vectorkids - beginning algebra - solve for x

Fractions
Thinking Blocks - Fractions
Match the Fraction - Fraction to Number Line
Fraction Models 
ABCya! | Adding Fractions with Like Denominators
Math Games: Fruit Shoot Fractions Addition
GapZappers
Triplets - Equivalent Fractions
Interactive Fraction Wall explore Fractions Percentages and Decimals
Kids, Fraction Tutorial, Learning Fractions - KidsOLR
Find Grampy
Identify Fractions with Number Line Models
Equivalent Fractions
Creature Capture Fraction Game 

Geometry
Math Game - Alien Angles
Measuring Angles with a Protractor
Quadrilateral Shapes - Geometry: Math Games
Geometry Game for Kids | Super Surveyor Geometry Instructions
GeoGebra

Measurement
Design a Party - Area and Perimeter

Addition and Subtraction
Cuisenaire Environment
LearningPlanet.com - SpaceyMath
Batter's Up Baseball (Math Games) 
Math Magician: Subtraction
Math Magician: Addition

Multiplication and Division
XtraMath
Product Game 
Batter's Up Baseball (Math Games) 
Math Magician: Division
Math Magician: Multiplication
Free Multiplication Games, Activities, & Math Resources | Multiplication.com
Factor Game
Concentration 

Coordinates
Billy Bug 

Graphs
Grapher