I've been looking for online animations of the EM fields in the nearfield
region of an antenna, and finally stumbled across a good one on an MIT
physics course site.
Don't miss the moving wood-grain or "DLIC" field plots. Load them onto
your hard drive, view with windows player, then switch on the repeat play
and set it for full screen. It's the "plywood" version of field
visualization.
(Note that the DLIC files are about 12meg each. They're worth it though.)