Kontact - Kontact is the integrated Personal Information Manager of KDE.
1CRM - 1CRM is an All-in-One CRM solution for sales, marketing, project and order management. Download 1CRM Free, and find out why it's right for your business.
Nextcloud Contacts - The Nextcloud contacts app is a user interface for Nextcloud's CardDAV server.
Pobuca Connect - Connect with your contacts.
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.
Contact Boss - CRM database management tool for managing contacts