Mercedes Jones and Santana Lopez, in season 2,episode 4, Duets
The whole glee club sings Push It in season 1 episode 2, Showmance.
The song Artie sings is Dancing With Myself
Sam sings Baby in the episode "Comeback".
Gwyneth Paltrow
Entitled "End Credits" (Made Famous by Glee Cast)
Rachel Berry (Lea Michele) sings taking chances
Jill Scott sings this classic. It has been also be redone by Glee.
Kristin Chenoweth
Vocal Adrenaline
Laryngitis!
Christina Perri is never on glee however rachel berry sings it in the prom episode
Idina Menzel or Shelby the Vocal Adrenaline's (competitive glee club) coach