A developer at CNET, author of the Mootorial, also built a lot of Mootools extensions. He recently released an update that fixed some bugs, but also added three new components:

• Fx.Marquee - does what it says, scrolls content in and out of an area, but with added fading and effects. It looks pretty nifty if you need a news ticker.
• IconMenu - at first looks like just another thumbnail scroller, but it allows users to manage a selection of items, such as shopping cart items.
• MooScroller - a cross-browser way to replace standard scrollbars with your own styled ones. It even supports the mousewheel event, which is necessary if you’re going to be replacing scrollbars with javascript.

If you haven’t already, be sure to check out all the other extensions he’s written.