Here is the Marvel Studios press release for The Avengers initiative.
"Meet the cast of S.H.I.E.L.D. and join The Avengers Initiative! Marvel Studios is to announce a S.H.I.E.L.D. Assembly in New York City for Spring 2011. During principal filming, S.H.I.E.L.D. will be out in full force in NYC to recruit and find new members. Cast members on hand include Samuel L. Jackson (Director Nick Fury), Clark Gregg (Agent Phil Coulson), Cobie Smulders (Agent Maria Hill) and Kevin Pennington (Agent Wendell Vaughn) and three Agents yet to be announced. Fans will get the chance to meet the stars and get their photograph taken with them at the event. Further Info will be provided in April or May. Fans who can't make it to NYC should not fret, something similar will happen at Comic Con in San Diego."
This event isn't "official" at this time. But sources close to the production have revealed that this is a legitimate event that will take place sometime this spring.
S.H.I.E.L.D. is in development and stars Samuel L. Jackson, Clark Gregg, Cobie Smulders, Kevin Pennington.
Marvel's The Avengers was released May 4th, 2012 and stars Robert Downey Jr., Chris Evans, Mark Ruffalo, Chris Hemsworth, Scarlett Johansson, Jeremy Renner, Tom Hiddleston, Clark Gregg. The film is directed by Joss Whedon.