This image from this video (at about the 9 minute mark) has been floating around various sites. It is our first look, as far as I or others can tell, of the auction house. As you can see the UI is dominated by various categories of items. These categories essentially lay out what is going on in trade. Interestingly most of the visible items appear to be crafting items with few exceptions. Of note is the grumble cake, which I assume is some sort of consumable.