YouMail - YouMail turns visual voicemail into a personal assistant for handling all your missed calls.
Tragofone - White-label VoIP Softphone with WebRTC and Auto-provisioning
Hi Voicemail - Stop robocallers filling up your voicemail
Lingo - Empower Creation and Ensure Brand Consistency. Build and Share libraries of visual assets with your entire team — all from your desktop.
MightyCall - Virtual phone system that lets you run your business from anywhere.
tSIP - tomeko.net/software: SIP client for Windows.