This should help:

http://paygsimwithdata.wikia.com/wiki/France

I was able to get an Orange SIM card in Paris, but I was never able to get a monthly plan to work without a contract or some other registration. I was able to get weekly unlimited Internet to work. The guy I was dealing with at the Orange store also said only weekly would work, but his English was almost as bad as my French.

Semaine Internet Max is the weekly plan, and you also need to get the mail access plan unless you want to just do webmail.

joe