Movie management, or MVC
One of the most used elements (by us) is the triad AppController - MovieManager - LocalController to handle multi-movie sites. Read on in Movie Management.
Translating, or multi-language sites
Sites that are deployed in more than one language can benefit from the Language Manager.
Trees and Arrays
Many types of data can be represented as trees. Tree and Tree Enumerator (API) offer ways to store and navigate tree structures.
Similarly, array enumerators take away the manual work of working with arrays. The usage of an Array enumerator (API) for controlling an image gallery is illustrated in the Thumb Controller demo.
ActionQueue: scripted animation and function flows
For scripting animations and basically all functions that need to be performed one by one: ActionQueue.
ASAP