According to the official Marvel site, and confirmed by show runners, cast and crew via Twitter, Marvel's Agents of S.H.I.E.L.D. has been renewed for a second season. Along side the show is the oft-discussed but never confirmed Agent Carter series, which has been ordered straight to a season order (skipping the formality of filming a pilot and running through the trials that many shows often have to endure).
Obviously this is great news for Marvel fans and fans of great genre television as it means not one but two more shows to look forward to this fall revolving around the extraordinary. For those that might have fallen off the Agents of S.H.I.E.L.D. train early in the season, I would really encourage you to go back and give it another try, especially in this post-Captain America: The Winter Soldier arc that the show is currently exploring.
For more information including casting as well as how many episodes to expect and when, I would expect ABC's upfronts presentation to reveal (at least some) answers. Stay tuned!