This is a small JavaScript application for visualizing different fractals such as the Mandelbrot set. More information is available in this blog post, where you can also leave comments.
Click to zoom in/out. The controls should be fairly self-explanatory, but be warned that zooming in and using larger image sizes increases render time (and might make Firefox go crazy). Use Safari with latest WebKit nightly for best performance. It uses the canvas element, so no IE support.