If you watched Agents of SHIELD last night, you saw a quick mention about the teaser trailer for Avengers: Age of Ultron, which was to air with next week's episode. And then the trailer leaked today.
Marvel, being savvy to a good thing when they see it, released this official HD version this evening. Hopefully, they'll seize on next week's SHIELD as an opportunity to show even more. The film's U.S. debut--in all it's Hulkbusting glory--is May 1, 2015.
Hat tip to io9.com