Yackpack is easy social voice messaging

The Social Software Weblog
"Yackpack is a social voice messaging service focused on ease of use they bill themselves as being usable by children as young as three. Your contacts are represented visually in your circle, and sending a voice message involves clicking on a friend (or clicking send to all), hitting record, speaking your message and hitting send. Your message then shows up in their message inbox. Nobody who is not in your circle of contacts can send you a message, thus avoiding spam."