This is the standards chapter in the Principles and Standards for School Mathematics (Standards 2000) of the National Council of Teachers of Mathematics. Select Geometry from the left column for across-the-grades standards. For specific grade level standards select Pre-K - 2, 3 - 5, or 6 - 8. (
http://standards.nctm.org/document/chapter3/index.htm
)
An series of interactives which allow the viewer to see the effect of various motions of figures on the plane, from the electronic examples of the Principles and Standards for School Mathematics. (Grades 6-8) (
http://standards.nctm.org/document/eexamples/chap6/6.4/index.htm
)