Nicole Atkins — "The Way It Is"
Here's the performance that earned Nicole Atkins a host of new fans. (The studio version is here, for comparison.) Here's her Wiki entry, official website and MySpace page. Her recent tour with The Pipettes must have been an interesting pairing.
I particularly enjoy the look on her face at the end, and hope that every performer has had that feeling at least once. In her case, it's her first solo national TV gig, and she knows she's absolutely nailed it.