Information on domestic flights in France is not easy to come by, one reason being that Air France has such a dominant position in France and already have flights on most internal routes.
Plus the French market is not as competitive. The French Railway system between major cities is both fast and competitive, especially if starting from Paris.
I have only been able to uncover a couple of airlines which offer domestic flights in France:-
http://www.easyjet.com/ - Toulouse to Lyon, Paris, Nice to Paris; Lyon to Biarritz, Bordeaux; Biarritz to Paris
http://www.twinjet.net/
Toulouse (32 Haute-Garonne, Midi-Pyrenees) to Metz/Nancy, Mulhouse, Brest; Marseille to Metz/Nancy, Mulhouse; Paris - Perigueux, Cherbourg
http://www.airlinair.fr/ Brest,(29 Finistere, Brittany) Bordeaux (33 Gironde, Aquitaine), Agen (47 Lot-et-Garonne, Aquitaine), Lyon (69 Rhone, Rhone-Alpes), Poitiers (86 Vienne, Poitou-Charentes), Brive (19 Correze, Limousin) Beziers (34 Herault, Languedoc-Roussillon) etc
http://www.ryanair.com/ now also has links from Marseille (13 Bouches-du-Rhone, Provence) to Lille (59 Nord, Nord-Pas de Calais) and Brest (29 Finistere, Brittany)
You can try sites like http://www.expedia.fr/ but even a price comparison site like http://www.baisse-de-prix.com/voyages.php seems to offer little new – it looks like Air France have cornered the market with little opportunity for discounting.
Most French autoroutes between major towns and cities are toll motorways, which whilst often offering fast and uncrowded dual-carriageways, can nevertheless add significantly to the cost of a trip through France - e.g over €90 (over £60) on a one-way trip from Calais to Nice (1226km of motorway driving about 760 miles).
However there are significant sections of autoroute which are toll free - most often these are around major towns and Cities (Paris, Bordeaux, Lyon etc).
In the North, the A16 is toll-free from Boulogne (J29) to the Belgian border (J36) via Calais and Dunkerque. The A25 from Dunkerque (J20) to Lille is free, so you can reach Lille from the main Channel ports without paying a toll!. Also all routes from Lille to the Belgian border.
The following autoroutes are toll free (as at September 2007)
A16 (part of the Autoroute des Estuaires (estuaries)) from Boulogne-sur-Mer (J29) to the Belgian border(J36)
A20 (L’Occitane) from Vierzon (J6 junction with A71) to Brive-la-Gaillarde (J53) via Chateauroux, Argenton and Limoges
A25 from Dunkerque (J20 with A16) to Lille
A28 from Abbeville (J1) to Rouen (J14)
A30/A31 (Autoroute de la Vallée de la Fensch) from Thionville (J1) to Toul (J12) via Metz and Nancy
A38 from Dijon (J33) to Pouilly-sur-Auxois (J24 and the junction with the A6)
A63 (Autoroute de la Cote Basque) from Bordeaux to Bellin-Bellet (J20)
A64 (la Pyreneenne) from St Martory (J20) to Muret (J25)
A68 (la Tarnaise) from Monastruc (J3 NE of Toulouse) to Albi (J11) via Gaillac
A75 (la Meridienne) from Clermont-Ferrand (J15) to Pezenas (J59) (except for the Millau Bridge) via Issoire
A77 (Autoroute de l’Arbre (trees)) from Pouilly (J26) to Nevers (J37)
A84 from Caen (J46) to Rennes (J25) via Avranches
