There's plenty of them, but mostly on the western side of the Azur coast. Eastern side is mostly cliffs (called calanques)
http://conferences.mongueurs.net/fpw2005/images/calanques01.jpg
though you find some sandy beaches there too. Camping on the beaches is forbidden but you have plenty of camping sites nearby.
On the east side, Bandol is a nice place, with a camping, small sandy beaches, and calanques.
For only sand, you have St Tropez of course, or Le Lavandou, Hyeres, or as said above Antibes or Cannes which are both expensive and without much camping room.
On the west side you have less well known places but just as nice, even up to the Pyrenees mountains. Here is a list of all the beaches you can find.
http://www.logassist.com/vacances/plages/herault.asp