My mother-in-law came up with a terrific ESL classroom discussion topic: "If you were to get the entire world together for a meal, what could you serve that everyone could eat?" (Note: This refers to cultural and religious restrictions, not allergies or food preferences.)
It's a fascinating exercise. When you come down to it, you pretty much get bread, fruit, some kinds of tea and water. But the discussion is the fun part (although moderating that discussion can be a little challenging, as respect for all the cultures involved must be maintained at all times.