The site lets you try problems and checks your answers. Trig - This site lets you interact with graphs and pictures of trig concepts. History and scientific applications of trig are discussed too. It assumes you're already familiar with the basic concepts, and just need to have things cleared up or refreshed. Very Fast Review - This site is poorly laid out but offers a helpful review of trig.
Answers are available.
Before Calculus - The material on this site is a brief review of the concepts you will need in order to understand more complicated topics in calculus. This interactive Java applet lets you play the piano using your mouse or your computer's keyboard. As you play the piano, you'll see the wave forms as well as hear them. The piano can also play a song for you, while you watch. Trig based chaos and fractals.