I bought one at my local Wal-Mart yesterday for $250 and they had several others on the shelf.
Before that, I went to Circuit City and was told they get shipments in a couple times a week - sometimes with none, sometimes with 15. However they said that Circuit City has some sort of agreement with Nintendo that no matter what day they come in, they are not made available for sale until the following Sunday. For that reason, they suggested that if I wanted one, to be at Circuit City on Sundays when it opens because they are first come, first served.
Hope that helps!