First up is Emmaüs, one of the biggest (and best) charity shops I have ever visited! This particular shop is open on Saturdays only (get there early for all of the best stuff), and is located up in the north-eastern 19th arrondissement. The charity was founded by Abbé Pierre in 1949 in order to help the homeless, some of whom are actually employed by the organisation, to help in the shop and in the processing of donations.
The shop itself is more like a giant warehouse, with a quirky-yet-tastefully-merchandised boutique-feel. The ceilings are high, the décor is bright and colourful, and large wooden structures artfully divide the huge space into specific zones. There is a section for second-hand haberdashery goods, men's, women's and children's clothing, white goods, other electronics, furniture, shoes, books and CDs, as well as a little vintage section. I even spotted a little knitting class taking place on some comfy looking sofas in a quiet corner. This place has everything you could ever want!
I left with some 60s flower-shaped elbow patches, a giant bag of buttons, some balls of wool and a chic little black cardigan, all for under €15.
42 Rue Riquet
75019 ParisSat: 10am-6pm
(I recently discovered another one, about a 5 minute walk away, over at the Centquatre):
104 bd d'Aubervilliers
Sat : 10am-7pm