The wavepacket simulator
The wavepacket simulator is a java applet which allows you to build up wave packets, either by manually inputting waves which are superimposed or by inputting a mean wave number and spread.
The medium through which the waves travel is dispersive.
The applet has three modes (auto-packet, manual and lecture). Lecture is probably the least useful as it is specific to a course taught here at Edinburgh, but it does show a nice example wave packet.
Acknowledgement and Disclaimer