I find Daily Python-URL one of my best sources for new and interesting software. It had a link to an article today with mention of three “interesting enterprise-ready open source applications”, particularly SugarCRM. Following up on this application with freshmeat I found a reference to another CRM, XRMS.
Both these applications look good, not quite as functional as Dark Horse CRM but because they are LAMP applications easier to modify and upgrade. Neither currently has a calender modules, though there is some talk of adding Wed Calender to XRMS.
SugarCRM seems to have a nice interface and more features for building relations between contacts but no file attachment ability. XRMS has a cleaner interface with the ability to add plugins.
I’ll have to look closer at the code for both applications before I decided which is the better to use.