Autotalent is a real-time pitch correction plug-in. You specify the notes that a singer is allowed to hit, and Autotalent makes sure that they do. You can also use Autotalent for more exotic (Cher / T-Pain) effects. It also can be used as a pitch shifter or for faux vocal doubling.
Oli Larkin did the VST/AU port of Tom Baran's open source pitch correction LADSPA plug-in. All credit goes to Tom for the algorithm. At the moment it is designed to be used on a mono track, if used on a stereo track, the left channel will be copied to the right.