Mumble - Mumble is an open source, low-latency, high quality voice chat software primarily intended for use...
FullContact Card Reader - Automagically scan biz cards into LinkedIn/Gmail contacts
Discord - Step up your game with a modern voice & text chat app. Crystal clear voice, multiple server and channel support, mobile apps, and more.
Google Contacts - Google Contacts is Google's contact management tool that is available in its free email service Gmail, as a standalone service, and as a part of Google's business-oriented suite of web apps Google Apps.
RaidCall - Free & Light. Setting up is fast and easy; with no need to rent or set up servers. Low CPU usage and minimum memory footprint allows for smooth, uninterrupted communication. im. Group Communication.
Nextcloud Contacts - The Nextcloud contacts app is a user interface for Nextcloud's CardDAV server.