Scott Cooper, John Lee Hancock, and Jason Reitman.
These directors might not be household names but the success of their limited filmography is working in their favors.
Scott Cooper's first picture would seem to be about to bring Jeff Bridges his first Oscar win (Crazy Heart). Not just that, but the film was shot in only 24 days.
John Lee Hancock 3rd picture surprised at the box office. Not only that was able to bring a popular actress, Sandra Bullock, a role with The Blind Side that has given her accolades and credibility she's never had including a likely Oscar nomination and a Golden Globe win.
Jason Reitman has brough celebrity status to Ellen Page in the surprise hit Juno, and now has given Anna Kendrick and Vera Farmiga award credibility as well with Up in The Air, not to mention provided George Clooney with a perfect part.
Not only are these young directors giving stars a chance to be invited to the big-kid-parties and a chance for the words "Academy Award winner/nominee" to be attached to their names, but there also creating positive roles, one's that people get excited about, that people attach themselves to. These aren't deglam projects like Charlize Theron in Monster, but performances that regular people will embrace as well.
Sure, if one of these directors have an unlucky break on a project or two, then there opportunities to sign big stars will deminish, but right now they're hot and I would think they have a lot of power to sign the stars they want on their projects.