These sites offer many examples of how symmetry works in a variety of shapes. Find out the difference between reflection and rotational symmetry. Includes interactive sites that let you draw symmetrical shapes and manipulate them. There is a link to an eThemes Resource on tessellations.
These sites explain how to create tessellations with polygons using rotation and reflection. Also includes information about artist M.C. Escher and examples of his tessellation artwork. There are several interactive games for manipulating patterns online.