Most current Voice/Video over IP (VoIP) systems are either highly centralized or dependent on IP multicast. We propose the Global Multimedia Collaboration System as a scalable, integrated and service-oriented VoIP conferencing system, based on a SOAP-based collaboration framework and advanced messaging oriented middleware. This system can provide media and session services to heterogeneous endpoints including H.323, SIP, Access Grid, and RealPlayer as well as accommodating diverse clients such as cellular phones. We suggest that our approach opens up new opportunities for extending classic VoIP systems by using these new technologies designed for scalable Internet based service-oriented computing. Copyright (C) 2006 John Wiley & Sons, Ltd.