Shodor Education Foundation
Shodor Interactivate: Lesson: Lines, Rays, Line Segments, & Planes
This robust lesson plan for upper elementary and middle school grades introduces the concepts for lines, rays, line segments, and planes. Resources are linked to it and ready for your use.
Oswego City School District
Regents Exam Prep Center: Reflection in a Line
This site gives some examples of line reflection transformations. Includes coordinate graphs to show reflections of lines and shapes.