http://www.pokemon.com/darkrai/
Nintendo will be releasing information on how to obtain Darkrai for the US. If it involves the Member Card (a key item in Diamond/Pearl), I already have one through an Action Replay. The Japanese gamers got a Darkrai with the movie release in theaters that had Dialga and Palkia's signature moves; Roar of Time (Dialga) and Spatial Rend (Palkia). Lucky Japanese...lol But that Darkrai wasn't in-game; it was downloaded at movie theaters.
Info on the releasement of Darkrai will be updated on the weblink I gave at the start of this thread. If anyone is interested in the movie which will be released in the US on DVD (it's the 10th movie), they are showing a sneak peek on Cartoon Network this coming Friday after a 3 new Pokemon Diamond and Pearl episodes.