They will be available at Gamestop as a free Mystery gift this month.
There are different times of availability for each one

Jan 3-9 is Raikou
Jan 17 -23 is Entei
Jan 31 - Feb 6 is Suicune

You can get this for Diamond, Pearl, Platinum, Heart Gold and Soul Silver but you must have obtained the pokedex in your game.

When these are transfered in to Pokemon Black or White you will unlock the chance to battle and catch Zoroark


*Got my Raikou today xd *