Sesame Street video archive from Sesame Workshop itself, searchable and keyword-tagged. It's not quite comprehensive (yet), but includes many Monsterpiece Theatre, Kermit's News Flashes, and Ernie & Bert sketches.
posted on Jan 1, 2008 - View this thread

Of Muppets and Men. [1 2 3 4 5 6] Excellent behind-the-scenes documentary showing the mental, verbal and physical athleticism of putting together The Muppet Show. Also, a TMBG video mashup with excerpts from the doc. [All YouTube, Previously]
posted on Aug 12, 2007 - View this thread

"It is an army bred for a single purpose; to destroy the world of men."
posted on Jun 4, 2007 - View this thread

Mah num ah num (Google Video) - The Muppets debut their first music video in 1976.
posted on Aug 17, 2006 - View this thread

The newist book from the world of Jim Henson about the man who spoke through puppets, I mean muppets.
posted on May 9, 2005 - View this thread