A flexible unified communications service for collaborative workgroups that can share files, import and export contacts and calendars from a wide variety of data sources and Web services, including Facebook, LinkedIn, and Google's Gmail. Entirely open-source based.

Price: Begins at $5/user/month for hosted version; $1095/yr for 25 users for server-based software version
Requirements: Works on a wide variety of browsers and operating systems. We tested it on IE 7, Firefox 3 and Mac Safari 4 in October 2009.

OpenXchange Inc.
303 South Broadway
Tarrytown, New York 10591
914 332-5720
http://ox.io