What is sumac used for? A friend of mine told me she uses sumac (I am not sure she was teasing me, or what).
Is sumac used in cuisine? If it is used, what is it used for?
Sumac is commonly used a tart flavoring element in the eastern Mediterranen region.  Historians believe that it was the common sour element in cooking for that area prior to domestication of lemons.  It is a characteristic seasoning element in Fatoush, a Syrian bread salad.

It's not usually available in the mainstream spice section of most grocery stores.  The best place to locate it is in mid-eastern markets, delis, upscale stores such as Dean &amp; Deluca or online through Penzey's or the Spice House.