beamer. But for some concepts, animations seem necessary.
How can one create PDF presentations in LaTeX, preferably with
beamer, which include animations that work on most PDF viewers?
Ideally, if the animations don't work then they should degrade gracefully. For instance, the first and last frame could still be shown.
\animate but this requires the PDF viewer to support showing several slides in succession, without manual intervention. Jens Nöckel suggests using external movies, which seems even less likely to work; this relies on a viewer being available for the movie format, and that the movie viewer can be called by the PDF viewer.
Older documents suggest MetaPost or animated GIF files, which seem hacky (though I will consider them if no other alternatives exist).
Please discuss only one main approach per answer.