One interesting project to keep an eye on is www.projectmayo.com and the 
OpenDivX they are developing. OpenDivX conforms to the MPEG4 standard that 
is targeted at web and mobility www.cselt.it/mpeg. This is lower bitrate
streams than John Macintosh's MPEGplugin, that is based on MPEG2 video
compression. MPEG2 is the base for TV and DVD etc.

(There are also emerging standards such as MPEG7 and MPEG21 that deal with 
media content and multi media to consider)

Karl