Fractions Model 
Fraction Game The object of the game is to get all of the markers to the right side of the game board, using as few cards as possible. 
Fraction Addition / Common Denominators Exercise 

Death to Decimals 

Fraction Model II  (In this version, the numerator and denominator can both take values up to 20.) http://illuminations.nctm.org/ActivityDetail.aspx?ID=44 
Fraction Model III  (In this version, the numerator and denominator can take values up to 100.) 