Fractal Lab, Interactive WebGL Fractal Explorer, is a very cool 3D web application. It can draw several types of fractals, both 3D and 2D, and it allows you to save the images produced.
The fractals are rendered using WebGL and GLSL with real time interactivity (at least for the simpler ones). The source code for the shaders is provided.
The number of iterations is configurable but beware the too many may hang up the whole system.