Columbus Guides
Includes a brief note on standard trading hours in Paris.
http://www.cityguide.travel-guides.com/cities/par/Business.asp

Fodor's.com
Details the opening times of shops and businesses in France.
http://www.fodors.com/features/stt/onbusiness/
france.cfm?page=Business+Hours&file=bizhours

Parisinfo.com
The opening hours museums, shops, transport, post offices, banks, etc.
http://www.parisinfo.com/guide_paris/rub5956.html

Things 2 Do in Paris.com
Covers everything from opening hours and electricity voltage to tipping and public holidays.
http://www.things2doinparis.com/CityGuide.php/category.26#26

World Executive
French business hours explained.
http://www.worldexecutive.com/cityguides/paris/business_tips.html

Yahoo!
Get the lowdown on French business hours.
http://travel.yahoo.com/p-travelguide-843126-paris_business_hours-i