The Apache Open For Business Project is an enterprise automation software project that includes ERP, CRM, E-Business/E-Commerce, SCM, MRP, and CMMS/EAM functions. It is a foundation and starting point for enterprise solutions and can certainly be used out of the box, but is also great for creating specialized applications.
GroupOffice is a groupware suite that takes your office online, implementing online collaboration and CRM. It allows you to share projects, calendars, files and email online with co-workers and clients. It is easy to use and fully customizable. It also features synchronization with PDAs and Outlook.