* [[Greg Egan]] has an excellent Java applet on [http://gregegan.customer.netspace.net.au/APPLETS/20/20.html his web site] that illustrates the apparent difference in group velocity from [[phase velocity]].
* [http://publicliterature.org/tools/group_and_phase_velocity/ Group and Phase Velocity] - Java applet with configurable group velocity and frequency.
* Maarten Ambaum has a [http://www.met.rdg.ac.uk/~sws97mha/Downstream/ webpage with movie] demonstrating the importance of group velocity to downstream development of weather systems.
