CoolSpeak

From First Ministry of Technology:

CoolSpeak is a free internet voice messaging service. Messages can consist of voice, text and file attachments. The system works through proxy servers and firewalls. Auto-update feature ensures you have the latest version. CoolCheck runs on your icon tray, informing you of any new messages. On-line directory makes it easy to find other users, and add them to the address book. Invite friends on to the system by using the simple invite function. CoolSpeak operates both on-line and off-line, has a simple interface, and is easy to set-up and use.