For US DVD releases (all Region 1), we have:
* The Muppet Movie (widescreen/fullscreen)
* The Great Muppet Caper (widescreen/fullscreen)
* The Muppets Take Manhattan (widescreen/fullscreen)
* A Muppet Christmas Carol (fullscreen)
* Muppet Treasure Island (fullscreen)
* Muppets From Space (widescreen/fullscreen)
* Kermit's Swamp Years (widescreen/fullscreen)
* A Muppet Family Christmas (fullscreen, as originally broadcast, edited, see FAQ)
* Emmet Otter's Jugband Christmas (fullscreen as originally broadcast, edited, see FAQ)
* Time-Life Best of the Muppet Show, Vol. 1-15 (volumes 5-15 only available from Time-Life, who don't ship overseas; volumes 1-4 available through Columbia Tristar and all regular outlets)
* Labyrinth (widescreen, available in regular or "Superbit")
* Dark Crystal (widescreen, available in regular or "Superbit")
Coming soon (on August 26):
* The Storyteller Collection (9 episodes)
* John Denver and the Muppets: Rocky Mountain Holiday
* Muppets Magic from the Ed Sullivan Show
And there are tons of Sesame Street DVDs as well, most notably (in my opinion) "Sesame Street Presents Follow That Bird" (fullscreen only) and "Christmas Eve on Sesame Street".
Hope this helps!
--Scott McGuire