Avengers Initiative

The Avenger Intiative is an intiative of S.H.I.E.L.D. responsible for the assembly of the Avengers.

Purpose
Although the exact purpose of the initiative has not been directly explained on-screen, it is implied that it employs people with special powers to defend the United States and humanity against threats.

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.