subblue. In addition to his Droste Effect, Fractal Explorer, 3D Mandelbulb fractal filter, and 4D Quaternion Julia Set Ray Tracer plug-ins that work in CS4+ (After Effects and Photoshop), he's added Little Planets.
This Little Planets filter applies a stereographic projection to a spherical panorama and makes it possible to seamlessly animate from a birds-eye view in the sky to that of a bug on the ground. You can get smooth warping between the planet and tunnel views by changing the latitude offset. He also has interactive demos, and points out an older implementation, Azimuthal projections.