Three new actors in the already large Fallout: New Vegas voice cast have been revealed at IMDb. None of them are particularly famous, but still. Chris Andrew Ciulla voices generic male ghouls (at least one ghoul, Raul, has his own voice actor - Danny Trejo) and various other characters, Ari Rubin voices Fantastic, a self-claimed technician working for the NCR (you can hear samples of his voice on his website), and finally the character or characters voiced by Halston Autumn McMurray are unknown so far.
Of course even more voice actors are probably yet to be revealed. For a list of all known actors so far, click here.