SugarCRM Community Edition

Operating System: Linux, Windows 2000/XP,Unix, BSD, or Mac OS X (and more)
Web Server: Apache , IIS , and other web servers that supports PHP
Database: MySQL version 4.0.x or 4.1.x (best 4.0.23)
Language: PHP versions 4.2.X or 4.3.X (best 4.3.10 ) or 5.X

SugarCRM is dedicated to placing the users and customers in control by abolishing the artificial restrictions imposed by vendors. Deploy SugarCRM On-Demand, On-Site or via an Appliance. Use Sugar Community Edition for free or pay for the commercial editions. Inspect and modify the source code. Create extensions that can be shared or protected. With Commercial Open Source, users are in charge.