From the Dept. of Computer Science at Swansea University, this is a java applet that will work on your computer screen (use a mouse) or on a iwb. Links to download, or use on the web, with movies of how it looks, and documentation pdf
interactive activities for practicing/learning addition, decimals, division, fractions, mental maths, multiplication, number patterns, percentages, problem solving, subtractions, the number system, using a calculator