SE-ScreenSavers!

A screensaver that displays the time using a flip clock.

Really Slick contains free 3D OpenGL screensavers. All of these savers are colorful and exhibit rich animation that never repeats. Some are based on classic screensaver themes, such as fireworks, swarms, and plasma. Others are more original and psychadelic, with geometric patterns based on principles of physics and mathematics. The screensavers are originally written for Windows, but the downloads page contains links to ports of other platforms such as Mac OS X and Linux.

Movable brick block screensaver resembling Tetris with Legos.

A truly "open source" screensaver that "types" its own code (or other selected text files) to the screen.