1)   Calcul 5.2.WIN32
Calcul will help your elementary school students practice mental arithmetic or to do fractions. Choose addition, subtraction, multiplication, division or fractions for an exercise.

 2)   CalculPro 1.2.0
CalculPro will help your elementary school students practice mental arithmetic or to do fractions. Choose addition, subtraction, multiplication, division or fractions for an exercise.

 3)   Valgetal Falling Numbers 3.22
Valgetal ("falling numbers" in Dutch) is an educational falling blocks-style math game with 20 progressively difficult levels for addition, subtraction, multiplication, and division. It is a clever twist on mathematical games and lots of fun.

 4)   MaTris 4.11.0515
MaTris is a nice program for practicing the basic operations of arithmetic. The calculation method is preselectable. It includes simple counting exercises, addition with symbols, addition/subtraction, multiplication and division.