CiviCRM - A Constituent relationship management for the Civic Sector
EspoCRM - EspoCRM is open source CRM (Customer Relationship Management) software that allows you to see, enter and evaluate all your company relationships regardless of the type.
Pipeliner CRM - Pipeliner CRM empowers small to medium-sized sales teams to close more deals and lower risk. Implementation and training are a breeze. Mac & Windows.
Less Annoying CRM - A simple customer relationship manager made just for small businesses. Manage contact info, track leads, and never miss a follow-up.
Odoo CRM - Open Source CRM
Zoho CRM - Omnichannel CRM for Businesses of all sizes