Vtiger
Vtiger is an open source CRM software that brings you the power needed to make your business run without boundaries. It is one of the most popular open source CRM solutions in the world, with over 4 million downloads to date. It has hundreds of thousands of users, plus an active community of developers working to make improvements so that you always get the quality CRM that you deserve. With Vtiger, you will be able to track your sales accurately and thus keep a closer eye on how your business is doing. You will also have the ability to manage your leads and contacts in the most efficient way possible so that you never miss out on a highly profitable sales opportunity. The open source edition has plugins that let the CRM work together with various applications that you use, like Thunderbird, Outlook and Office.