I wrote the Mandelbrot Explorer to explore new features of HTML5. It makes use of both the canvas element and web workers.
You can click and drag to select portions of the mandelbrot set to view in greater detail. You can also also choose alternate gradient maps. The gradient maps are simply 1x256 px images where each pixel contains a color that maps to the width value.
After peforming a pass through the fractal you can click "generate video" to create a smooth playback of your progress through the set.