i dunno about stores but i got my black 60gb one...so freakin tyte i cant stop drooling hahah....i think the black 60gb ones were so popular that apple stores havent even gotten them in yet...my local on has every kind except the black 60gb ones
I can't speak to Best Buy in specific but it does seem as if the 30 gig white units are the ones showing up at most stores around the nation. Some places have black ones and some have 60 gig units too so all the variations are shipping. I think that the scarcity of the 60 gig black and, to a lesser extent the white is due to the fact that large chunks of the original shipments are being sold to people who reserved iPods before they hit the shelves. At least, IMO.
Best strategy: look at a lot of places and look frequently. Don't believe them when you call them and they say they don't have them. Go to the actual store and look.