Links to some of the sites I check up on every day in no particular order:

XviD.org Home of the XviD video codec.
doom9.org Doom9 is the master of guides and info on how to backup a DVD.
Nic's builds (old url) Another place to get binarys of the great XviD codec.
Koepi's Homepage Alot of info on XviD.  Very usefull site.
Avih's XviD page Information on XviD.
Avih's filter This is Avi h's post processing page.  There you can get his post-processing filter.
tomshardware.com A hardware news website.  Very frequently updated.
theregister.co.uk All the latest technology news in one great page.
VirtualDub.org The best encoder and video editor for AVI known to mankind.
XviD.net XviD compression informaiton in Spanish