France e Keys
Information on finding medical assistance in Paris.
http://www.francekeys.com/english/general/health.shtml

Intransit International.com
Details numbers for every emergency ranging from tooth ache to gas leaks.
http://www.intransit-international.com/life_paris_emergency.html

La Prefecture de Police au Services des Parisiens
Official website of the Parisian police force. It's in French only, but you can click on the link marked "Les points d'accueil", to search for police stations by arrondissement.
http://www.prefecture-police-paris.interieur.gouv.fr/default.htm

Magic Paris
Contains a whole host of useful telephone numbers.
http://www.smartweb.fr/SurvivalTips/STipsUITelephone.asp

ParisBy.com
A comprehensive list of emergency contact numbers.
http://www.parisby.com/tourist/tour8.htm

Paris Tourist Office
Includes the contact details of the city's main police stations.
http://www.paris-touristoffice.com/va2/services/pratique.html

US Embassy Paris
Useful emergency numbers. In PDF format.
http://www.amb-usa.fr/consul/guideoas/emergency.pdf

Yahoo.com
Numbers you should dial if there is an emergency.
http://travel.yahoo.com/p-travelguide-843130-paris_emergencies-i