Vtiger
Vtiger is one of the best open source CRM software solutions available today, combining powerful sales and help desk function into one system. The CRM is trusted by over 100,000 businesses around the globe and the number of organizations deploying it is growing every day. The open source version is free to use forever with no licensing or monthly fees. The software can be installed on a local or cloud-based server running Linux or Windows, then made available through an organization's internal network or through the public Internet. The software comes with all of the sales management features expected from a high-quality CRM, including sales automation, contact management, collaboration, appointment scheduling, one-click emails or phone calls. For businesses who provide after-sales service to their customers, it also has a full help desk section with automatic case creation from customer contacts, a support pipeline showing the status of each case, automatic case escalation and more.