Hostels in France are called "Auberges de Jeunesse". Not as many as you would find in South East Asia but nevertheless quite a few.
In the summer there are many campsites across the country which can be a good and cheap alternative.
AirB&B is also becoming popular in France and it is working very well, you can really find great places to stay at very reasonable prices.
Though check out Couchsurfing also which is a great free alternative to hostels and a great way to meet new people!
PS in Cassis if you want to visit the Calanques there is an amazing Auberge called Les heures claires just in the village.