There a bunch of things you can do with the Moo Tools Library, but lets name a few anyway:

Forms and Scripts to enhance them:

Highlighter for elements

Calendar

Validator or Validator

Ajax and Username

If you want more ideas of what to do with them - here are over 300.

http://www.1stwebdesigner.com/recources/300-jquery-css-mootools-and-js-navigation-menus/

You may ask why as being a web designer I do not write more, tutorialized articles, well me, like yourself, wants to save time. I am doing this in my free time from school and work so that hopefully it will save you time. There is no point to re-invent the wheel. If it has been done, modify it to your needs, but give credit where credit is due!

I originally found some of the sources above from here.