Maybe this is common knowledge, though I thought I would share this. Say you record vocals on track 1, and they are not terribly pitchy. Pitch correct the track 1 vocal, and put the pitch corrected track on track 2 (leaving the original non-pitch corrected vocals at track 1). If you play it back now, it probably sounds odd. The trick is shifting one of the tracks forward (in time) anywhere between say .005 to .030 seconds (it pays to experiment). Not only does it give a pseudo double-tracking effect for fuller vocals, it often sounds better to me than just the pitch-corrected vocal track by itself. Very often, when I do real double-tracking vocals, my timing is not tight enough & it sounds sloppy (I realize timing-correction could help, though I haven't tried that yet).