Here are The Traveling Professor's favorite food markets in Paris.

Marché Raspail.  Rue Cherche Midi/Rue de Rennes in the 6th.  Rennes or Babylone métro station.  It’s an organic food market on Sunday from 9 to 3.  On Tuesday and Fridays from 7 to 2:30 it offers a wider variety of products.   It’s easy to get to, the vendors are friendly and I have found items other than foods such as wicker baskets and flowers.   Consider filling up at an ATM and taking the short walk to La Grande Épicerie at Bon Marché, part of the famous department store (not open Sunday), a gourmand’s paradise. 

Marché Montorgeuil.  Rue Montorgeuil in the 2nd.  Located near the Les Halles métro, this one is from the good old days.  I like to go here to taste, touch and smell, then sit down at one of the many restaurants serving fresh dishes with market ingredients.  Open Tuesday and Sunday until 6 p.m.

Marché Iéna (aka Marché Président Wilson).  I just discovered this one on my last small group tour to Paris.  I was taking the bus to the Eiffel Tower and noticed the flowers and market stalls.  I got off the bus and was treated to all sorts of meals being cooked for on-the-spot-consumption.  They had it all - choucroute garnie, crepes, all sorts of cheeses, moules (mussels), onion soup and a lot more.  

Marché Bastille.  The diversity of this market at one of the crossroads of the city makes it so interesting.  I’ve sampled Lebanese, African, Mid Eastern, and Asian alongside a bounty of local offerings.  Open Thursdays and Sunday until about 2 p.m.  Métro: République.