Global IP Sound (GIPS), the engine behind a whole bunch of VoIP services such as Skype just added VoiceMail capabilities to its products. The new VoiceMail Engine, which allows applications developers to quickly and successfully build a fully-functional and high-quality voicemail application for VoIP telephony systems. GIPS VoiceMail Engine is a server-based solution. From what I understand this is more catered to meet the needs of the enterprise, than anything else.