Add fun Snapchat filters to your Mac camera
Just like Whatsapp but from your Mac's desktop
Proteus Project
Unofficial desktop client for Facebook chat
End-to-end encrypted communication
iOS's iMessage now also on Mac OS
Vector Creations Limited
Mattermost
A single program for all your IM accounts
Chat with your Yahoo and MSN Messenger contacts
64Gram
TSIT
Gajim Developers
Ferdi
Chat with friends on this multiplatform messaging client
Multiplatform IM client
Brett Terpstra
A traditional chat with group videoconferencing
Yuuguu Ltd
An IM combo born of Mozilla and Pidgin
Google
Danny
Talk to all of your MSN contact even with your Mac
Carlo Gandolfi y Paolo Portalu
Aurelio Jargas
Cooperative whiteboard and voice communication through Jabber
Add a bunch of improvements to iChat
AOL's instant messaging program
A Multiprotocol Instant Messenger client
Open Source alternative to chat with MSN contacts
A simple Jabber-based IM client
Share files and chat with friends safely