Zoom - Equip your team with tools designed to collaborate, connect, and engage with teammates and customers, no matter where you’re located, all in one platform.
Sitecake - Drag and drop CMS for HTML websites. It's flat file CMS so it's pretty fast.
Telegram - Telegram is a messaging app with a focus on speed and security. It’s superfast, simple and free.
Anchor CMS - Free and lightweight blogging system
WhatsApp - WhatsApp Messenger: More than 1 billion people in over 180 countries use WhatsApp to stay in touch with friends and family, anytime and anywhere.
Textpattern - Textpattern is an elegant content management system that is free, open source software.