Here's proof that physics can be fun. This student-created site explores how sound waves travel, and includes several neat Java applets which demonstrate phenomena like the Doppler effect. You'll need a computer with a sound card to get the full effect. Students can work with the material at a variety of levels. Though the quality of these applets is uneven, the site is well worth a look since it could easily be used in either individual or group settings.
Students can change data input to observe the changes in the simulations.
It explains terms simply by clicking on the words to receive definitions. The site also includes an online quiz function for students to test themselves on new material explained within the site or in your class. A question of the week greets you when you log on, and answers are supplied weekly. It could be useful for student review or supplemental material. The site is expanding and may include more at a later date.