It's an external harddisk made by Lacie, in the shape of the lego bricks. If you have several, you can stack them together. Though the price is a little bit higher then normal, The prices vary from $89.99 to $189.99. Despite that you can choose from three different colors: white, red and blue.
Well, a company named ZIP ZIP finally made a lego usb brick in the form of a 2x4 brick. It's 1GB big, but wears a hefty pricetag of aus $59 (roughly $49 us bucks). I'll rather make my own, just like Brett.