Good deals & clothes
The sales take place twice a year: the winter sales in January and February, and the summer sales in July.
Also consult the sites (between individuals) for good deals:
https://www.leboncoin.fr (general site)
https://www.vinted.fr (second-hand clothing)
https://www.momox-shop.fr (second-hand books, CDs and video games)
Secours Populaire
Secours Catholique
Entraide and Solidarité
La Fraternité