Snapvine lets people leave each other voicemails online. The contacter calls a central Snapvine number, then enters in a code corresponding to the person they are trying to contact, and leaves their message. Alternatively, you can leave messages using a microphone connected to your computer. The voicemails are then played from simple embeddable widgets. Messages can either be public, and can be listened to by anyone who visits the page in which the widget is embedded, or they can be private and only heard by the contactee.
Snapvine is popular on Myspace and similar social networks, especially between artists or celebrities and their fans.