In voice over IP (VoIP) networks, the Session Initiation Protocol (SIP) encourages the convergence of telephony and web-based services. The web-based phone has become an attractive tool for developing VoIP services. In this paper, freewares are used to build VoIP platforms providing the web-based phone, voice, video, instant messaging (IM) and prepaid services. A billing system and webpages are also developed for an administrator providing administrative functions. The VoIP users can also see their call detail records in real time. Conducted experiments show that our system can accommodate 400 calls per second without loss. If the bottleneck component is located at a standalone server, this number is nearly doubled.