Vtiger
Vtiger is an open source CRM software that is extremely popular among small and medium-sized organizations all over the world. As an open source product, using it is completely free and it can be deployed to an on-premise or cloud server. The Vtiger CRM software application is also offered by some shared web hosting providers to their clients. This flexibility allows users to deploy the CRM in the environment of their choice and ensure they'll have access to their data from anywhere with an Internet connection. The Vtiger open source CRM platform is regularly maintained by its developers, as well as thousands of independent contributors to the project scattered across over a hundred countries. They provide support to users on the Vtiger community forums, regularly release updates and patches for the CRM, in addition to creating various kinds of extensions and plugins to increase its functionality.