GTKMathplot is an interactive plotting program based on GTK+ and the Cairo graphics library. It can display bidimensional curves, tridimensional curves, and surfaces from Cartesian or parametric equations describing the mathematical objects you would like to visualize. It is designed to be intuitive for high school students with good mathematical knowledge. University students of engineering, physics, mathematics, or natural sciences should need no explanation at all to start using it proficiently.
DeforaOS Locker is a screensaver application, available for desktop and embedded environments alike. Written for the DeforaOS platform, it supports a plugin system for authentication, animations, or generic extension. It can notably reuse xscreensaver demos, or integrate a terminal as background animation while being active.