phplist.com : phpList : The world's most popular open source email campaign manager
openSUSE.org
OpenSSL: The Open Source toolkit for SSL/TLS
Open source live support - Mibew Web Messenger
Open Geospatial Consortium OGC(R)
Open Computing Facility at University of California, Berkeley
OASIS Advancing open standards for the information society
MySQL :: The world's most popular open source database
mod_ssl: The Apache Interface to OpenSSL
Internet Security or DNS Service for your Business or Home - OpenDNS
Drupal - Open Source CMS drupal.org
DOAJ -- Directory of Open Access Journals
Center for Democracy & Technology Keeping the Internet Open, Innovative and Free
BioMed Central The Open Access Publisher
Apache OpenOffice Downloads
Zimbra offers Open Source email server software and shared calendar for Linux and the Mac.
Zimbra provides open source email and calendar groupware software, Zimbra is a popular choice for Linux and Mac OS X email servers and supports SaaS deployment, appliances and virtualization platforms.
Open Society Foundations (OSF)
The Open Society Foundations work to build vibrant and tolerant democracies whose governments are accountable to their citizens.