vtiger CRM is an Open Source CRM software for small and medium businesses. vtiger CRM uses open source technologies such as Apache, MySQL, PHP (and other open source projects) to provide a powerful multi-platform CRM solution (works on Linux and Windows).

vtiger CRM provides the CRM features that other commercial programs sell for thousands of dollars, such as: sales force automation, customer support & service, marketing automation (with support for e-mail campaigns), inventory management (with product customization module), security management, and of course contact management and task scheduling.

Prophet, developed by Avidian Technologies, is a CRM add-on that enhances Outlooks productivity by adding more advanced CRM features. It comes in two major editions: Individual (for single use, has three other sub-editions - Personal/Advanced/Premium) and Server (for team use, has two other sub-editions - Professional Server and Enterprise Server). Prophet is integrated into Outlook, so when adding an appointment, contact or a task that is added into your Outlook database too (no need to synchronize like with other external CRM programs).

Heap CRM is a customer relationship management application with modules like messaging, calendars and contacts. You can create reports on this data, or export the data, all in a web based interface that lets you administrate your customer relationships.

ZOHO CRM, developed by AdventNet Inc., is an on-demand CRM solution that offers sales and marketing tools, customer support solutions, integrated inventory management, possibility to create CRM reports and Outlook integration via the provided Outlook plugin.