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.
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.
Upcoming.org is a social event calendar, completely driven by people like you. Manage your events, share events with friends and family, and syndicate your calendar to your own site.
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.