SugarCRM one of the leading Open Source customer relationship management (CRM) software available with three different editions which allows the organisation / user to choose as per the requirements.
SugarCRM Community edition: SugarCRM community edition is freely downloadable from the SugarCRM website http://www.sugarcrm.com/crm/ ; SugarCRM free version allows a user/manager to maintain the customer lead, Opportunity, Sales, lead tracking, marketing automation, managing accounts etc.
Sugar Professional: SugarCRM Professional version is very much ideal for small and Midsized of businesses. Sugar Professional is not a freely available, but on a per user licence basis.
Sugar Enterprise: SugarCRM Enterprise is ideally targeted to large organisation where advance level of CRM is required for decision making. Sugar Enterprise is little costlier as compared to Sugar Professional with some add on features such as customer Portal, workflow etc.
SugarCRM Product comparison Matrix is divided as per the User Experience, Sales Force Automation, Customer Support, Reporting & so . .on for a detail information you can check on the following link: http://media.sugarcrm.com/datasheets/EditionsComparison.pdf