Butte-Aux-Cailles, in the 13th, is very different from the rest of Paris. The architecture is different and it has a real village feel. The 13th is home to a large immigrant population, so when you get off the metro here you can indulge in any number of good and cheap ethnic eats.
On Saturdays there's also a huge open-air market near the Place d'Italie where I bought some jewelry for the girls back home. Also a good place to sample and snack.
There are a number of shops in Butte-aux-Cailles. Easily one of the most charming is the "honey place." This tiny shop is dedicated to all things related to bee-keeping and honey. You'll find beeswax candles, honey soap, every kind of honey imaginable in all sizes of jars (some of it from the owner's own hives), artisan crafted glass honey drippers. Oh, and some pretty amazing homemade pain d'epices (now I know why Clothilde Dusolier raves about it in her book) in big and small loaves. Pick up an assortment of these goodies to make a honey of gift bag for the folks back home. The owner is also quite nice and soft-spoken.
There are a lot of good restaurants in this neighborhood, but you won't find a more popular lunch spot than Le Temps des Cerises, a very French café where you'll sit cheek by jowl with Parisians. The only English I heard spoken here was by my table mate who interrupted his French conversation to help me order my steak au point (medium). Great three course lunch menu, VERY reasonably priced. Nothing fancy. I highly recommend the bavette steak which comes with great Roquefort sauce and a pile of some of the best frites I've every had and the pear clafoutis for dessert.