Avengers Initiative

The Avengers Initiative is an operation of S.H.I.E.L.D. responsible for the formation of the Avengers.

Background
Although the exact purpose of the initiative has not been directly explained on-screen, it is implied that it employs people with special powers and abilities to defend the United States and against threats that may be too complicated to handle.

The Avengers Initiative is said to have once been been scrapped in favour of "Phase 2", which involves using the Red Skull's research of the Tesseract to develop and distribute weapons of mass destruction to combat extraterrestrial attacks, following the arrival of the Destroyer and Thor in New Mexico.

The operation was unofficially reactivated by Nick Fury when Loki emerged as an international threat.

Involvement
Those involved with the Avenger Initiative include:

Nick Fury
Fury is the director of S.H.I.E.L.D. who takes personal interest in the Avenger Initiative

Natasha Romanoff
Romanoff investigates the suitability of Tony Stark for the Avenger Initiative under the name of Natalie Rushmann.

Tony Stark
Stark is brought on as a consultant for the Iron Man suit by Nick Fury.

Phil Coulson
Coulson contacts Stark about his escape from the Ten Rings in Afghanistan and discovers Mjolnir in a New Mexican desert.

Erik Selvig
Selvig is brought in after the being involved in New Mexico, Fury ask him to looked on The Cosmic Cube.

Steve Rogers
Rogers was recruited by Fury for a new mission.

Maria Hill
Nick Fury's right-hand woman.

Trivia

 * The Avengers Initiative has a lot of resemblance to the Ultimates program in the limited series The Ultimates, in that the group is formed as a government-sponsored team to combat the threat of the Chitauri.