Flexible open-source content management and blogging software with an active user and developer community and a wide variety of plug-ins or extensions available.
Full-featured open source office productivity suite, featuring word processor, spreadsheet, presentation, drawing and database packages; free MS Office replacement.
Inkscape is an Open Source vector graphics editor, with capabilities similar to Illustrator, Freehand, CorelDraw, or Xara X using the W3C standard Scalable Vector Graphics (SVG) file format.
Social networking for non-social purposes with a focus on professional development, networking for jobs and problem solving through the expertise of those in your extended network.
Scribus is an open-source program that brings award-winning professional page layout to Linux/Unix, MacOS X and Windows desktops with a combination of "press-ready" output and new approaches to page layout.
Domain management in multi-platform environments (Windows + Linux + Mac, etc) including user management, printer management, shared folder management, etc.
Eclipse is an open source community whose projects are focused on providing an extensible development platform and application frameworks for building software.
The Social Source Commons is a “knowledge commons” that provides users with: a directory of software applications; links to relevant documentation, localization tools, services, user reviews; and a place to request tools/features.