
Both FBTB.net and ToysNBricks.com posted details this morning.
I would appear that if you spend $11.99 or more on a LEGO Star Wars set, then you get one of these guys for free. This is true on-line and in stores. It would also appear that you can buy these guys separately on-line for $2.99 apiece.
I'd suggest going down to your local Toys R Us today, look for the new Prince of Persia sets, and potentially pick up a chrome stormtrooper to boot (albeit you'll have to buy a LEGO Star Wars set too)!
(Picture from Toys R Us website)