Empathy - Apps/Empathy - GNOME Wiki!
TeamViewer - TeamViewer lets you establish a connection to any PC or server within just a few seconds.
Adium - Adium is a free instant messaging application for Mac OS X that can connect to AIM, MSN, Jabber, Yahoo, and more.
AnyDesk - AnyDesk is the world's most comfortable remote desktop application. Access all your programs, documents and files from anywhere, without having to entrust your data to a cloud service.
IM+ - Chat everywhere! IM+ is the most widely used mobile IM app! Connect all-in-one to MSN, Yahoo!, Goo...
LogMeIn - LogMeIn gives you fast, easy remote access to your PC or Mac from your browser, desktop and mobile...