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.
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.
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.