WHMCS - WHMCS is an all-in-one client management, billing & support system for online businesses.
Bitrix24 - Bitrix24 is a free (for small businesses) social enterprise platform. It is a united work space which handles the many aspects of daily operations and tasks. Create your own social intranet in minutes!
HostBill - HostBill is a powerful and flexible, all-in-one automation, billing, client management and support platform for online businesses.
VOGSY - Professional service automation tool built on Google G Suite
Blesta - Blesta is professional client management, billing, and support software.
Office Timesheets - Professional Services Automation