From Tom Whittaker:
This applet can be used for simple animation of two or more images--you can allow your visitors to have no controls, or a full-set of controls: stop & start; set animation speed; single step frames and change direction of animation sequence; go directly to the first or last frame; movie looping or 'rocking' modes. It also allows overlays of other images--if you want to put a map base and some plots or analyses on top of a satellite image, for example. Checkboxes are used to select/un-select overlays. Fade between images--using 8 bit, alpha-component. A slider may be used, or the fading may be animated.