I've been using Falstad's freeware Java applets for teaching acoustics and oscillation concepts in the classroom for years now. I recently decided to give Crocodile Clips' Yenka Light and Sound modeling software a try after some of my own children enjoyed using it in school. At first it was to take advantage of the free license for home use (yes, FREE). Now, however, I'm going to use it in classes thanks to the numerous models already built-in and even more content online. My favorite built-in model so far is "Speed of Sound" - which lets you add other media, such as vacuum, water, and wood, and see how the speed of sound changes and then interacts with the sound wave in air, assuming it exits the extra media at all - very cool!
Not to leave optics out, there are informative models for angles of reflection, refraction, mirrors, lenses, telescopes, and more. For instance, to show that the angle of incidence equals the angle of reflection, the student drags two protractors into the workspace and measures both angles as the (virtual) beam of light bounces off the mirror. Simple, but effective. Many more sophisticated models are available too, plus you can build your own and save them for later use (as an educator, I like that).
Yenka also covers more than the physics of sound and light - mathematics, chemistry, computers, electronics, and other packages are also available. I've tried the chemistry package with my boys. Being boys, they were particularly pleased with being able to experiment with (virtual) dangerous substances after having to suffer through the kid-safe chemistry sets sold in stores these days.
Crocodile Clips is based in the UK, so American and other visitors to their website may not understand the references to terminology used in the British education system. Luckily, the laws of physics do not change as a result of the software leaving the UK! Yenka is a free download for students to use at home. Use outside of the home requires buying a license, of course. Finally, it works on Mac and Windows operating systems.