I love World Harvest! They have a huge selection of stuff, but I most often go here for a handful of things:
-Falafel sandwiches
-Cheese. For a given type of cheese, it is usually cheaper here than the grocery store, and of course the selection is far superior.
-Halal meats, but especially sausage. Italian sausage, soujuk, and merguez are all usually available here.
-Olives
The staff is really helpful and will answer any questions about their huge and sometimes bewildering selection.