Dr. Geo is an interactive geometry program that is distributed as a universal portable application. It allows one to create a geometric sketch and manipulate it according to its constraints. It is usable at home or at school, in primary or secondary education. It is simple and effective with extended features including scripting and programming.
AbulEdu Calcul Mental is a software tool that trains children in mental calculation as stipulated by the French Ministry of Education for primary schools. Activities include addition, subtraction, multiplication of integers, addition tables (+2 to +9), times tables (x2 to x9), additional additives (to 10, to 100, to 1000), multiples (of 5, 10, 15, 20, 25 and 50), and orders of magnitude (with additions, subtractions, and multiplications). There is also an editor and selective launcher.
QMentat helps you practice mental arithmetic. It uses arbitrary-length fixed point arithmetic, and can handle any size numbers, only limited by the size of your screen (and in the case of division with an integer result, the speed at which the number can be factored). It is also quite configurable, allowing you to tailor the questions to your needs.