Instant Messaging

Messenger for Desktop icon
Unofficial desktop client for Facebook chat
Camfrog icon
A traditional chat with group videoconferencing
Retroshare icon
Share files and chat with friends safely
Messages icon
iOS's iMessage now also on Mac OS
Franz icon
A single program for all your IM accounts
Coccinella icon
Cooperative whiteboard and voice communication through Jabber
AIM for Mac icon
AOL's instant messaging program
Nimbuzz! icon
Chat with friends on this multiplatform messaging client
Line icon
Just like Whatsapp but from your Mac's desktop
Palringo icon
Multiplatform IM client