At long last, 343 Industries has released Halo 3: ODST for all owners of Halo: The Master Chief Collection. If you ordered MCC early enough, then ODST is free for you to download! If you got it a bit later, then ODST will be available for purchase for just $4.99 (USD).

In addition to this, the Remnant multiplayer map was released today for Halo 2: Anniversary.
Halo 3: ODST Campaign Enhanced for a New Generation