According to that site, the Densha Otaku clip was done by Gonzo, which apparently was founded by former Gainax members(and started out doing PSX FMVs - it shows). I have a love/hate relationship with that studio, They can make some good things, but they mostly over use CGI while not developing story much. That, and their fan's (self-labeled Gonzo Whores)are rather annoying. I haven't seen the that show though.

http://www.catsuka.com/interf/bideo/amateur.htm

That has the other Daicon animations.