I am not a espert freeride but i'm really interested in it, and i'm really looking forward to begin alpine skiing next year.
The most famous freeride tracks are in:
Others tracks are in the Brenta group on "Dolomiti del Brenta" group.
But you can find the best tracks in Aosta Valley, more precisely in the nearby of Alagna.
skirama for wood skiing and powder (and some nice big mountain skiing in passo del tonale)
dolomiti superski for steep skiing
be aware that off piste skiing is proibited in italy so be sure that police and security do not see you when skiing off piste especially in the arabba and canazei area. In andalo and folgarida usally the police does not bother you that much but in marilleva there are some restricted areas that are national park