"Franz is your messaging app / former Emperor of Austria and combines chat & messaging services into one application. Franz currently supports Slack, WhatsApp, WeChat, HipChat, Facebook Messenger, Telegram, Google Hangouts, GroupMe, Skype and many more. You can download Franz for free for Mac & Windows."
Modern Messaging
Fast, flexible messaging for Mac, PC, iPhone, iPad & Android. Archived and organized as you go, with configurable alerts, notifications and sync so you never miss a beat.
'Keybase is a new and free security app for mobile phones and computers. For the geeks among us: it's open source and powered by public-key cryptography. Keybase is for anyone. Imagine a Slack for the whole world, except end-to-end encrypted across all your devices. Or a Team Dropbox where the server can't leak your files or be hacked.'
"Break through
Riot allows teams to communicate across a wide range of collaboration apps. If some team members use Riot while others use IRC, Slack or Gitter, Riot will allow these team members to seamlessly work together. Riot offers the richest network of communication bridges."
"From group messages and video calls all the way to helpdesk killer features. Our goal is to become the number one cross-platform open source chat solution."
"All-in-one voice and text chat for gamers that's free, secure, and works on both your desktop and phone. Stop paying for TeamSpeak servers and hassling with Skype. Simplify your life."