National Council of Teachers of Mathematics
The Math Forum: The Four Basic Symmetries
This is a site from the Math Forum that gives visual examples to show the differences between the four different kinds of symmetry. Examples are given along with links to additional information.
University of Regina (Canada)
University of Regina: Math Central: Symmetry and Translations
This University of Regina site gives some history and definitions about translations and symmetry.
CK-12 Foundation
Ck 12: Geometry: Composition of Transformations Study Guide
This study guide on the composition of transformations covers some vocabulary terms and different types of these compositions. It is available for download with free registration.