Vtiger
Vtiger is a leading open source CRM software platform, offering an effective way to manage your customer interactions without having to pay any up-front license fees or monthly usage fees. All that you have to do is install the software on your own in-house or cloud server. Vtiger can be installed on both Windows and Linux servers for added flexibility. While the open source edition doesn't come with technical support like the hosted one, all users get free access to a knowledgebase and discussion forums that are very active. If you ever run into a problem, all you need to do is make a post and one of the members will likely have a solution. This CRM has both sales and customer service management functions, which is very handy if your organization also provides after-sales support. The interface is neatly laid out, allowing your team members to instantly get access to the information they need to get the job done.