I have written an applet for demonstrating reflections and rotations of a function about the x and y axes, and origin. I was unable to embed the applet in my blog, but it is embedded on the class wiki, here. The explanation of how to use the applet is with it on the wiki page.
I can see a couple of instructive uses for this applet. One use is as a demonstration tool during a lecture. A second use is as an independent study tool for students to explore symmetry and reflection of functions.