Here's a terrific idea for using pattern blocks to teach symmetry.
Here's a nice anchor chart for symmetry.
Here's a page on finding and drawing lines of symmetry.
Here's another mandala lesson focusing on lines of symmetry.
Here's a simple set of cards showing line symmetry.
This site has a number of projects focused on symmetry. Directions are easy to follow and use readily available materials.
Here's a nice anchor chart on symmetry.
Here's a post with some ideas for folding symmetrical origami creations.
Great journal entry for teaching about symmetry.
Here's a terrific video on symmetry that looks at the science of symmetry and explains how the symmetry of animals tells us more about them.