I recently came across a great TED talk by social scientist Amy Cuddy titled Your body language shapes who you are. Her research shows that simply adopting a power posture for two minutes can increase your testosterone, reduce your stress hormone cortisol and make you more powerful in social situations... all of which translates into greater self-confidence.
She goes on to describe how to overcome the feeling of being a fraud not just by faking it until you make it, but by faking it until your become it.
From now on, I'm walking around my unit with my arms in a power pose. I don't care what the neighbors think! Check it out: