From October 15th (today) to October 30th, Mew will be available as a Wi-Fi download. It it level 5, knows no special moves, and unlocks no events in your games, but hey, it's a Mew.
http://bulbanews.bulbagarden.net/wiki/Mew_distribution_starts_on_October_15th
I'LL TOTALLY REMEMBER TO GET IT THIS TIME