jQuery.Stacky lets you create UIs with panels that open horizontally using jQuery. It requires jQuery 1.7 or higher.
Panels can be opened, closed, expanded and collapsed. A panel can be opened either next to a given panel or a the end, in regular mode (pushed next to a panel) or in floating mode (absolute position). Additionally, the open and close events can optionally call functions to, for instance, set or retrieve data to/from panels. Basically, this is how it looks: