These are great websites for help in practicing math facts!
 
Flashcard Practice
http://www.aplusmath.com/Flashcards/

Find the Hidden Picture Addition Practice
http://www.aplusmath.com/games/picture/AddPicture.html

Addition Concentration
http://www.aplusmath.com/Games/Concentration/Addition_Concentration.html

Place Value Practice
http://www.funbrain.com/tens/index.html

Word Problem Practice
http://www.funbrain.com/guess2/index.html

Subtraction Hidden Picture Game
http://www.aplusmath.com/games/picture/SubPicture.html

Number Line Game
http://www.funbrain.com/linejump/index.html

Estimation and Rounding
http://www.aaamath.com/est.html

Math Baseball
http://www.funbrain.com/math/index.html

Speed Math
http://www.mrnussbaum.com/speedmath.htm

Arithmetic Attack
http://www.math.com/students/practice/arithmeticpractice.htm

Math Fact Cafe (make flashcards or view pre-made ones)
http://www.mathfactcafe.com/

Multiplication Practice
http://www.aaaknow.com/mul.htm