SplitMenu is a static menu option that displays parents in the header and children in the sidebar.
When a mobile, or equivalent device, with a small screen is detected, the menu becomes a selectbox.
Fusion is a CSS dropdown menu system, enhanced by Mootools, such as its animations and transitions.
Features include multiple columns with individual width / distribution settings, inline icons and subtext, as well as item grouping. All are configurable on a per item basis.