Had a great little weekend stay in Christine's flat in Belleville. The neighbourhood is quiet and there are local amenities (boulangeries, bistrots etc.) nearby. It's quick and direct to get to the city centre with the nearby metro line 11. Parc de Buttes-Chaumont is delightful, and also very close to Christine's apartment.
Highly recommended if you'd like a good-value place for a cute weekend in Paris :)