Freeware Programs: Xponaut
Download DoNaut

DoNaut  Add-on for instant messengers and internet phone software. Change and add effects to your voice, sound like anything from a big giant to a little chipmunk. Share your favorite music when you calling your friends.

Download Voice Tweaker 4.1

Voice Tweaker 4.1  The Voice Tweaker plug-in is a harmonic pitch transposer designed for monophonic signals such as voice, spoken or sung, or solo instruments