I have loved Juno ever since I first saw it. It is still easily one of my favourite films.
Meet Juno (Ellen Page) - a witty teenager who accidently becomes pregnant by her shy, nerdy friend Paulie (Michael Cera). The film follows the story of her pregnancy, starting with her almost-abortion & ending with the adoption of her baby. It sounds deep & depressing, but I promise it is not. It is actually fairly heartwarming.
If you're into well-written indie / teen comedies, Juno is for you.