There are fourteen total.

1. Diaruga - Steel/Dragon type - Obtained as main legendary on Diamond
2. Parukia - Water/Dragon type - Obtained as main legendary on Pearl
3. Yukishii - Psychic - Part of this series Trio of Pokemon. This one is yellow.*
4. Agunumu - Psychic - Part of this series Trio of Pokemon. This one is blue.*
5. Emuritto - Psychic - Part of this series Trio of Pokemon. This one is pink.* **
6. Hiidoran - Fire/Steel - You must have National Dex.
7. Regigigas - Normal - Upload or trade over all three Regis.
8. Giratina - Ghost/Dragon - National Dex needed. 3rd Dragon.
9. Kureseria - Psychic - National Dex Needed **
10. Fione - Water - Pokemon Ranger Game is needed to get. ***
11. Manaphey - Water - Pokemon Ranger Game is needed to get. ***
12. Darkrai - Dark - Event Pokemon
13. Shemi - Grass - Event
14. Aruseus - Normal - Event****

*The legendary Trio is described by some to be the Mew Trio. They come after you have dealt with your version specific Legendary
** They are like the Jhotto Legendaries.
***To get Manphey, you must have doen the event in Pokemon Ranger to get Manphey's egg. Over in Japan, this mission was an event mission, but their is a rumor it is built into the game. You hatch the Egg and get a LV1 Manaphy. You also can breed it with Ditto to get Fione.
****In the game you will find plates floating around. This Pokemons ability alows it to change type acording to which plate you give it.