Discord
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.
Share photos, videos, music, files, documents and more between all of your devices. File sharing from phone to PC, phone to phone, PC to phone, PC to tablet.
Zoom is an easy, reliable cloud platform for video and audio conferencing, chat, and webinars across mobile, desktop, and room systems.
WhatsApp for web is a platform independent messaging app which allows you to communicate for free.
WhatsApp for PC is a cross-platform mobile messaging app which allows you to exchange messages without having to pay for SMS.
Mobile messenger app with free voice & video call over 3G/4G & Wi-Fi.
Thunderbird is email and calendar software by Mozilla (the maker of Firefox) that offers the same functionality as the (commercial) office application Microsoft Outlook.
Slack simplifies business communication. It brings all your team's communication together, giving everyone a shared workspace where conversations are organized and accessible.