Graviboard is one of those tweaks. This tweak will take devices application icons that are sitting at the top of the screen and after the user makes a particular gesture, these icons fall to the bottom of the screen. The icons can be moved around either by touching the icons or by using the accelerometer.
There is another tweak called Motion that is really kind of neat. Similar to the Graviboard in that you can move icons around, it allows the user to apply various effects to the different icons. You can rotate an icon, flip an icon, have an icon jump, use transparency with an icon, apply either a vertical or horizontal wave to the icon to name just a few of the effects.
You can download this tweak and will be activated once it is downloaded. Configuration is done by way of a preference entry found in the native settings application. It is possible that additional effects or options could be added later on. Something that this tweak also does is to randomly apply the effects to various icons intermittently. Talk about a crazy looking Springboard!
You can get Motion found in the Big Boss repository for $1.00. In order to make it run, you will need to a device that has been jail broken.