sphere, a vocal idol group released by Music Ray'n after Light Voice Girls became a big hit. Members include Aioi Toyosaki, Yao Tosatsu (Asuna), Nanako Shoumi, and Kayo Takagaki. ceased activity as of 2018.
trysail, also a voice idol group from the house of Music Ray'n. Members include Amamiya Ten (voice of Tokyo Ghoul and Friend of the Week heroine), Momo Asakura, and Natsukawa Shiina. It's kind of the usual Music Ray'n family formula of starting with a popular voice actor and moving on to a singer idol afterward.
There's also wake up girl and idol master, both of which are voice actor idol groups derived from anime.