Going 'Chiner'[she nai] in the 'Marché aux Puces' is a popular Parisian week-end activity, unearthing antiques and all kind of bric-à-brac as well as second-hand clothing. A nice stroll into popular Parisian folklore, right outside of Paris city limits in St Ouen
It takes place from Porte de St Ouen to Porte de Clignancourt 18th arr. Sat. Sun. and Mon. 9am to 6pm.

Fleas are jumping along the boulevard périphérique and way deep into the town of St Ouen. The oldest and most popular flea market of Paris divided in several markets, second-hand or brand new cloth, military surplus in Marché Malik, antiques in Marché Serpette and others. A full range of display from scraps to luxurious antiquaries is what characterizes St Ouen flea market.

Also in Montreuil, Sat., Sun.  and Mon. 7:30am to 5pm
Exotic fleas, from Africa mostly, old clothes as well as second hand goods of all kind, 'les Puces de Montreuil' take you back to the roots of flea market, as St Ouen used to be in the old days.

Vanves, on Sat. and Sun. 8.30am to 1pm, is more for real bric à brac, very popular among neighboring Africans, a lot of bargains.

And for the fanatic of the exquisite French taste, the specialized markets :

The Marché aux timbres (stamps market) located at Rond-point des Champs-Elysées, 8th arr. Every Thurs., Sat. and Sun. and public holidays from 10am to sunset.
This is where philatelists, postcards and coins collectors, professionals & amateurs display their collections, buy and sell, Rond-point des Champs-Elysées, 8th arr.

Also, several Marché aux fleurs (Flower market), generally open Tues. through Sat. The most famous ones are located  Place Louis Lépine on the Ile de la Cité, Place de la Madeleine and  Place des Ternes.

For the lovers of animals, the Marché aux oiseaux (bird market)
These bird-markets are located pretty close to each other at Place Louis Lépine, Ile de la Cité 4th arr. next to the flower market on Sun 9am to 7pm and  Quai de la Mégisserie 1er arr. (Seine Banks) organized in a series of pets shops open every day.

Finally, the Fabric and clothing market at Marché Carreau du temple, rue Perrée 3ème arr. It is a traditional roofed market like one can still find in middle-east with excellent bargains and the Marché St Pierre 18th arr whereThe famous Montmartre stores are displaying clothing, tapestry and curtain fabric, suiting every wallet.