I think most properties will charge you for parking, even on the outskirts of the city and particularly at La Défense. Street parking may be available, but it is usually paying every day (except from 7PM to 9AM) but Sunday and August.

I have friends who have stayed at the Marriott Courtyard in Neuilly-sur-Seine and they liked it quite a bit (on-site parking is €14.50 per day):

http://marriott.com/property/propertyPage/PARCY