On the second weekend of September it is the Circuit des Remparts in Angouleme. It is on Friday 14th, Saturday15th and Sunday16th of September 2012.
I will be there and will take lots of photos but for now here are the posters from the last 10 years, ( For the purists 2002 is not available so I put an earlier one in and they are in no particular order) . You can purchase these at the event or from the web site. They cost 20 euros each which is not bad.
The web address is http://www.circuit-des-remparts.com/ and there you can find all the details about what is on and where.