Purple Math
Purplemath: Trigonometric Functions and Their Graphs
Explains the horizontal forms of trigonometric graphs by showing how they relate to the circular graphs.
Interactive Mathematics
Interactive Mathematics: Graphs of Sine and Cosine Functions
An interactive graph provides a demonstration to show how the measure of an angle is related to the sine and cosine waves. Topics covered include amplitude and period. Examples allow students to practice the concepts.
Pennsylvania State University
Kettering University: Vibration & Waves
A short tutorial providing general information about waves, their categories, properties and behaviors. Includes several animations and some practice questions with answers.
Other
Personal Site: Sine and Cosine Do "The Wave"
This personal site provides a great animation of how the sine and cosine waves are formed. It connects the unit circle with the sine and cosine graph.