Math

A+ Math 
Here you can do flashcards with adding, subtracting, rounding, multiplying and dividing on the computer! The game will tell you if the answer is correct, and if you get it wrong, it tells you the right one. (There are two forms of cards; one requires Java, and one does not) 

AAAMath.com
This site lets you review concepts and practice them online. It scores you and tells you the correct answers. The concepts include most taught in Grade 4. 

Adjustable Spinner 
Here you can practice probability by playing with a spinner that you can change. 

Comparison Estimator 
You can try estimating the number of items in a box. The game will tell you whether or not you are right! 

Factorize
In this game you create an array that demonstrates the factors of a number given to you by the computer. After each correct answer you get to demonstrate another set of factors. When you have all of the factors, a happy face will appear. 

Fraction Sorter
This is a little harder than the previous site. Here you make the same fractions, but you have to drag to sort them to the right place on the number line. 

KidZone Free Printable Worksheets - Grades 4 - 5
This site has lots of printable Math worksheets. 

Math Baseball 
This site lets you play baseball using basic facts to score runs! 

More or Less Estimator
You calculate whether the area of an unusual shape is larger or smaller than a regular shape they show you. 

Pattern Creator 
You can practice making a pattern by completing the pattern started for you. 

Print and Learn Math Sheets 
Here you can print out lots of worksheets to practice Math skills at home. 

Spinner  
This game lets you practice estimating probability by using a spinner. You can make an estimate, change the number of sections in the spinner and then spin to see if you have made a good prediction. 

Teacher Link from Utah State University
This site has very large downloadable workbooks that let you add, subtract, multiply and divide. You will have to print these on your printer to do the worksheets. There are some handwriting worksheets as well, but they only have capital letters.

Understanding Experimental Probability
This game lets you try different ways to explore the probability of a spinner or dice landing on a certain color or number. The game tallies the results so you can see how you are doing with your estimates! 

Science 

Light and Shadow Experiments You Can Do At Home
These are experiments with light that you can do at home: Afterimage, Blind Spot, Colored Shadows, Diffraction, Fading Dot, Up Periscope, Making a Sun Clock, Pictures from Light, Pringles Camera 

How Stuff Works - How Light Works 
This site has lots of information about what light is and how it works.