Macaw is a Free Program That Helps Add Text Tracks to QuickTime Video.
Macaw Directions (screen capture videos)
Sample Transcript and Video
A sample transcript for Macaw and a short video for practice.
Toggle Buttons (Macintosh or Windows)
Free QuickTime sprites which you can add to your QuickTime videos to let users toggle on and off the text track. There is also a version that lets you toggle English and Spanish captions on and off.