Eurolines coach travel, one of the less costly ways of getting around France, have just made things easier by introducing Isilines (www.isilines.fr), a new coach service offering exceedingly cheap fares that enable you to travel between small French towns on routes that avoid the main cities – something you can't do if you travel by rail.
Fares are variable and, obviously, depend on dates, but it's easy enough to compute from their website what is available. But Paris to Toulouse, for example, costs as little as €18 (one-way), while a trip to Marseille can be as cheap as €38. If you arrive in France at Calais, then the trip to Paris can be as little as €18.
Coaches are comfortable and well-equipped, with free WiFi, electricity and USB outlets, fold-down tables, personal air conditioning and light control (similar to what you'll find on an aircraft), and large reclining seats. Moreover, there is no charge for luggage.
All stations are in city centres, but this can be a great way to see the countryside at a rather more genteel pace than on a TGV; so, it's perfect if you are not in a hurry, or, more especially, on a budget.