Mac OS X Softwares to Instant Messaging

QuteCom, formerly WengoPhone, was a free and open-source VoIP client supporting the SIP protocol. It enabled users to make voice and video calls, send instant messages, and connect with contacts across various networks, including Google Talk.

Blink is a robust, real-time communications client leveraging the SIP protocol for secure and private instant messaging, voice, and video calls. It emphasizes features like end-to-end encryption, file sharing, and screen sharing across various platforms.

X-Lite is a popular and free VoIP softphone application designed for making voice and video calls over the internet. Leveraging the Session Initiation Protocol (SIP), it provides a straightforward and reliable way to communicate with other SIP-enabled devices and services.

Spark is a free, open-source instant messaging client optimized for businesses and organizations. It integrates seamlessly with Openfire servers and supports a wide range of features including group chat, file transfers, and screen sharing, making it a versatile communication tool.

ooVoo is a comprehensive video chat and instant messaging client designed for seamless communication across various platforms. It offers a suite of features including high-quality video calls, group conferencing, screen sharing, and instant messaging.

Nimbuzz is a comprehensive cross-platform communication application that provides free instant messaging, voice calls, and social networking features. It connects users across various devices and platforms, enabling communication with friends and family globally.