XScreenSaver
XScreenSaver is a screensaver program for Unix-like operating systems running the X Window System. It is maintained by Jamie Zawinski. Open source Unix-like systems such as Linux use it almost universally.One reason for XScreenSaver's tremendous popularity is the ease of adding extra modules, known as "hacks". The program's home page states "Any X program that can draw on the root window can be used with xscreensaver."