Some resources for ideas

http://www.chow.com/recipes/category/quick-and-easy

Chowhound Boards: Office Potluck

http://101cookbooks.com/

http://smittenkitchen.com/

http://www.davidlebovitz.com/

Maybe some sort of topping (spinach cream cheese, soft cheese, roasted vegetables, sliced meats, hummus as per SirJman) over slices of good quality, crusty bread? The toppings may need to be bought last minute or held in a cooler.