Marvel's Agents of S.H.I.E.L.D. Teaser [Vine]
EDIT (9:54pm): Embedded the full trailer above.
It's being written and directed by Joss Whedon, takes place in the same Marvel Cinematic Universe as The Avengers and Iron Man 3, stars Clark Gregg as Agent Phil Coulson (Spoiler: who is supposed to be dead) and an early look at the show will be airing tonight during the season finale of Once Upon A Time on ABC and I'm hyped to see it.
(Source: The Verge. Source of full trailer: BleedingCool.com)