Heliomonde (mentioned in the above posting) is a naturist site!
We've stayed at Camping International at Maisons Lafitte - which is a just about OK campsite, in a beautiful suburb of Paris, and near to a train station. It's alongside the Seine, pitches are a good size, but the toilet blocks (when we last were there some years ago) could have done with a bit of TLC.
We've also stayed at Huttopia at Rambouillet - a bit further out still, and liked that site - although it's very wooded and shady. Toilet facilities were first class though. Also takes Camping Cheques.