The following Java Applet was programmed by some of my students (Jared Maguire, Marc Reichman, Jeff Saunder and later also by Chris Keenan and Tom Ross) to fulfill an assignment requirement. This applet produces some of the best orbit diagram pictures I've ever seen.
To zoom in on a certain area of the Orbit Diagram, you can either type specific bounds for x and the parameter c, or more conveniently, you can use the mouse to select a rectangle in the diagram - the applet automatically zooms in on that rectangle. Pressing the Reset button will pick good starting windows for the family that you've chosen. Please be patient as the applet produces the diagram; the speed of the applet depends on the client system.