The Human-Computer Interaction Lab.University of Maryland, has released new versions of the Piccolo framework for Java and .NET and came up with a new web site.Piccolo (and its predecessor Jazz) are very cool graphics frameworks that allow you to make good use of zooming in your 2d application. The resulting applications are called ZUIs (zoomable user interfaces) or 2.5d applications.
E.g. Jef Raskin’s book “The Humane Interface” presents such an application of a hospital that uses semantic zooming (showing the appropriate level of detail at various zooming scales).
You might start with a map of the country, showing all hospitals. If you zoom in on a hospital at some scale you start to see the rooms. If you zoom further, at some scale you see the beds in the room. If you continue, you might see details of the patients.
If you are familiar with 3d programming, using powerful libraries like OpenGL or Java3D, you already know how useful concepts like coordinate transformations and scence graphs are to structure your graphics. Piccolo makes these concepts available for the 2d realm.