Cabri allows to drag some of objects on the picture plane simply by mouse and then change initial settings of the construction, which can bring new insight into the problem.
Cabri can animate movement of some geometrical objects and show their trace or locus. Dynamics is very powerful tool of this software.
Completed Cabri figures you can place into www page as a CabriJava applett (with help of CabriWeb application). Both you can download from www.cabri.net site.
Some of our pages containing CabriJava appletts you can see here: