We first reported on the potential series last month, although it wasn't immediately clear what the show would focus on. While the report did indicate it would take place in the same world as Marvel's The Avengers, it may not feature the same superhero characters. The show will center solely on, "the activities of the top-secret S.H.I.E.L.D. espionage organization featured in The Avengers."
It was said, though, that Joss Whedon does reserve the right to throw tie-ins from the movies into the show. It still isn't known if Samuel L. Jackson will be featured in any capacity as S.H.I.E.L.D.'s Nick Fury.
Joss Whedon is co-writing the pilot script with Jed Whedon and Maurissa Tancharoen, both of whom will serve as showrunners if the pilot is picked up to series. They will executive produce with Jeph Loeb and Jeffrey Bell. Joss Whedon is expected to direct the pilot episode, if he can fit it into his schedule.
The series is moving fast, so it's quite possible that we will see S.H.I.E.L.D. sometime in 2013.