This is from my 3D space screensaver "Planet Quest", which has been doing well on download.com recently. Please download from here:
The main features of this screensaver are that the visuals (textures and geometry) are 100% created procedurally on-the-fly in a worker thread. Therefore there is no repetition, and scene change is basically instantaneous. Also, no OpenGL extensions are used so it can run on reasonably low-end hardware. However, it is fillrate-bound and runs at the native desktop resolution, so doesn't perform brilliantly on the lower-end hardware.
Visuals include: planets, clouds, moons, suns, supernovae, stars, nebulae, galaxies, planetary rings, asteroids, comets, lens flares. All procedural.
For version 4.0 I've done a lot of refactoring; for one thing, it dawned on me that in the previous version, memory fragmentation was a problem. I also do my own error dialog with minidumps on exceptions and advice to the user (it is a free-trial software).
Naturally I'd love any feedback!