The new Cataclysm trailer can be found on the official WoW Media site, if you haven't seen it yet. The video showcases fly-bys of the Old World zones that will be ravaged by the Cataclysm event, including the Barrens and Darkshore. The trailer also shows off some impressive in-game footage of the new Goblin and Worgen classes, and their respective starting zones.
Screenshots, artwork and wallpaper media are also available, including an epic-looking glimpse at Deathwing, the character that the upcoming expansion revolves around. Stay tuned for more news and media, and remember to check out our Cataclysm Wiki for the most up-to-date info regarding the upcoming expansion.
The official Cataclysm website is also live. It doesn't feature too much additional info and media beyond the aforementioned vids, screens and artwork, although it will serve as a repository for any upcoming official announcements, so you'll want to keep it bookmarked.