CITATION(Mayken @ 18/09/2006, 12:37)

But please be aware that these skates are only tolerated by the police if the group is smaller than 20 people, if they skate on sidewalks and respect traffic rules. All others can be apprehended by the police.
That's the theory. In actual fact, I have never gotten into trouble with the authorities in a few years of nightly skates in the streets of Paris (on the streets, not the sidewalks).
Among the "wild rides" that I know of:
Monday : "speed" skate. Unsure of the details, it's above my level, they're real crazies.
Tuesday : "Belette" -- a quite technical ride, cobblestones, small passages, stairs,... with a good pace. Meeting at "Bourse" at 20:30.
Wednesday : "WCR" -- good paced ride. Meeting at "Opera Bastille" at 21:00. The founder has left Paris, so this ride may or may not continue, depending who shows up...
Also on Wednesday: "RSI" - a more "official" ride, on the sidewalks and with marshalls. Beginner/intermediate level. I think they start at 21:00 at the shop "Vertical Line" (métro Bastille).