Citizens of Switzerland or of the European Economic Area do NOT need any visa to enter France, no matter what the purpose or the duration of the stay is.
This rule applies to citizens of the following countries:
Citizens of the E.E.A. may enter :
Citizens of E.E.A. may move to metropolitan France and the D.O.M.  with just a valid national identity card or a valid passport. Citizens of the above listed countries are no longer required to obtain a visa or a residence permit (" carte de séjour ") to live in France.
Exception: if you are over 18 years old, hold a passport from Cyprus, Czech Republic, Estonia, Hungary, Latvia, Lithuania, Malta, Poland, Slovakia or Slovenia AND if you wish to work in France, you will still have to apply for a residence permit ("carte de séjour pour ressortissant européen") within two months after arrival in France at the Préfecture of city of residence. Note that it is always advisable to contact the Préfecture BEFORE leaving the U.S., in order to get a complete list of documents to provide to apply for such permit.
Please note that you do not need any visa to enter and live in France for longer than 3 months if :
you hold a valid U.S. passport
and you are the legal spouse (marriage certificate) or child (under 18y.o.) of a citizen of the above listed countries
and you are accompanying your spouse / parent who is also moving to France.
However, you will have to apply for the residence permit ("carte de séjour pour membre de famille d’un ressortissant européen") within 2 months of entry into France, at the Préfecture of city of residence. Note that it is always advisable to contact the Préfecture BEFORE leaving the U.S., in order to get a complete list of documents to provide to apply for such permit.
Last update: 05/22/2009
 Overseas Departments (D.O.M.) : Guadeloupe, Martinique, Saint-Martin, Saint-Barthélémy, Guyane & Réunion
 Overseas Territories (TOM) : New-Caledonia, Polynesia, Wallis & Futuna, Mayotte and Saint-Pierre-et-Miquelon