The Pharrell Collaboration including the Stan Smiths and Track Jackets released today and they are selling out fast. As of the time of this post we have not seen them on the US site, but they have shown up on the UK site as well as many of the online boutique stores. Here is a list of some of the stores that are carrying this collection:
Also check local adidas Originals stores for this collection as well.
Update: The list above was for the Pharrell Stan Smiths. The Pharrell 50 Supercolor Superstars were released on the main website as well as adidas stores and many sneaker stores such as Foot Locker and Finish Line but they have also sold out at most stores in all of the colors.