A list of examples is available here: Web-based Simulator Examples
The Transfer Function Simulator above is a simplistic (yet quite powerful) imitation of commercial products such as Simulink(r) by MathWorks(c) or PLECS(r) by PLEXIM(c). The purpose behind providing the simulator is simple: not everyone has access to Simulink. Alternatively, there might not a free license at the time or simply one would like to explore the design of control systems online on a machine without a MatLab installation.
Extensive documentation is available here: Web-based Simulator documentation
Change log is available here: Web-based Simulator change log