They are all at Gametrailers, and all fo the 358/2 Days videos have been out for quite some time, as for the Birth By Sleep, it just surfaced on the web, and it looks soooo good, it almost puts 358/2 Days close to shame...but not...
Links:
EPIC Birth By Sleep -
http://www.gametrailers.com/video/japanese-epic-kingdom-hearts/55472
Agrabah Showcase -
http://www.gametrailers.com/video/aggrabah-showcase-kingdom-hearts/55456
Battle Gameplay -
http://www.gametrailers.com/video/battle-gameplay-kingdom-hearts/55458
Beast's Caslte Showcase -
http://www.gametrailers.com/video/beast-castle-kingdom-hearts/55457
Cutscene after Darkside battle #1 -
http://www.gametrailers.com/video/xion-gameplay-kingdom-hearts/55459