Interactive Periodic Table with images

http://images-of-elements.com/ - very good site

Maths: Geometry - Rotation

This is really helpful. You can use this interactive tool to rotate 3 different shapes by various degrees. You can even change the point of rotation - and then it shows you step-by-step how the shape rotates (Each point moving in a circle/arc around the centre).

http://www.mathsisfun.com/geometry/rotation.html