MooTools is released under the Open Source MIT license, which gives you the possibility to use it and modify it in every circumstance freely, very similar to the jQuery library.
Here is one cool example of how to make your navigation menu smoothly glow on a mouse hover.
Here’s a great light-weight slider from MooTools that offers simplicity, elegance, and smooth transitions.
A very useful too for your search fields, the AutoCompleter script from MooTools can add that little extra that will make the browsing experience more enjoyable and user-friendly.
If you want to dynamically generate an image reflection on your site, the Reflection.js script is what you have been looking for. This is the same script used in the jQuery library. Many scripts like this overlap in both the MooTools and jQuery frameworks.
Based on ajax, this small widget allows to integrate many many bookmarks for every post on your blog, website etc.
By clicking the mooSocialize button, a window will appear, which lets you choose your favorite network. Having a thumbnail of each service beside the link, it’s easy to see and find the one of your liking.
But that’s not all – it doesn’t redirect you to that page, but opens up the page in a hovered layer. Convenient and easy. On top of the opened layer is a small “x”, which allows to close the window later on.