Note: All these scripts are experimential and merely proof of concepts. They are neither tested thoughly, nor neccessarily compatible with all browsers (I don't want to care about IE when playing around). Most of them are using the trunk version of MooTools of the date they're created, hence they're most likely incompatible with your version of MooTools, but it shouldn't be hard to update them.

License: Use the scripts as you like, but I would be glad if you give me credit, mail me where you used them and/or donate me a coke or two ;-)

A-Star
The A* path finding algorithm implemented in MooTools.
Fx.Selector
Experimential Addon to MooTools (some version aroung 1.1) allowing CSS rules to be passed to all MooTools' Effect classes.
Expander
Experiment for a 'more' button. To be used for spoilers, code snippets, comments, whatever.
List Filter
A textmate like filter. A search for 'motol' matches 'MOoTOoLs' as well as 'MOcha TOtaL'.
Fx.Counter
Example for a simple Class extending Fx.
Fx.Explode
Experimential multi-element effect.
Input Replacements
Some input widgets, like a tag input.
SimpleSlideShow
Very minimalistic slideshow class.
Swiff.Video
My first steps with Flash. It uses Swiff to play .swf files from JS.
Transform
Transforms the input from a textarea to a new place. I don't know a better name for this.