Kaleider manipulates images to emulate various Kaleidoscope, Mirroring, 3D Mirroring and Funneling effects.  It is a capable graphics tool for people who are interested in symmetry, tiling, tessellation and mosaic patterns, with controls for manipulating images and tiles.  Effects can be shifted interactively by clicking and dragging with the mouse, essentially re-rendering the same effect based on different relative positions within the source image, so that you can experiment with the results and decide when a picture suits your taste.

Aside from any usefulness though, Kaleider is really just entertaining and fascinating to watch while in Automatic Effects mode, with an endless variety of randomly selected effects wandering across the screen according to randomly selected patterns.  The Rooms feature exhibits Kaleider patterns in 3D perspectives, optionally with automated Roaming motion.  With Mask/Mandala enabled, evolving patterns are mingled with a static background color or image.  This visual experience can also be accompanied by music from the built-in Audio Player.  Kaleider display sequences can be captured to Video, and actions can be Scripted to create choreographed performances of dynamic art, optionally controlled via a MIDI device.

The Kaleider Screensaver is also free!