Dates to avoid when going France (shops might be shut).

January 1st,
Easter Monday (in 2011: 25th April) (though not Good Friday except in Alsace),
May 1st - La fête du travail, labour day
May 8th - Armistice day, World War II
Ascension Thursday,
July 14th, French national holiday, Bastille day
August 15th, Summer holiday day
November 1st, Toussaint, All souls' day
November 11th, Remembrance Day, Armistice of World War I
December 25th, Christmas. (though not Boxing Day, December 26th)