Based on the concept of physical manipulatives such as blocks and Cuisenaire rods , manipulatives are physical objects which embody abstract mathematical concepts. Virtual ones are virtual representations of physical objects which embody abstract concepts Brilliant! Animated GIF's illustrate a large number of mathematics concepts. National Library of Virtual Manipulatives WisWeb is the website of the Freudenthal Institute for secondary education (students of 12 to 18 years old). The main focus of the site are applets; small computer programs that run over the internet These activities are designed for either group or individual exploration into concepts from middle school mathematics. The activities are Java applets and as such require a java-capable browser. contains visual poetry and science fun narrated in an object oriented graphic environment, open source Flash modules