From Drupal and Moodle, right through to a Git versioning system and Perl modules on CPAN, we contribute back to over 175 community open source projects. This list is in order of the number of projects contributed to.
Drupal (contributions) (http://drupal.org/)
Drupal is an open source content management platform, allowing an individual or a community of users to easily publish, manage and organize a great variety of content on a website. Equipped with a powerful blend of features, Drupal is able to support community sites, blogs, portals and more. This is the contributions repository containing contributed modules, themes, translations and installation profiles. You can find the Drupal core project at http://ohloh.net/projects/3189. Since drupal.org moved from CVS to Git, this summary contributions project is no longer representative of contributed activity because each project has its own repository instead of one, large shared one. Ohloh added a Drupal contributions logo for maintainers to list their projects separately.
Koha Migration Toolbox (https://gitorious.org/koha-migration-toolbox)
A collection of scripts and tools for migrating from legacy library systems to Koha.
A rewrite of the Moodle question engine
XML graph engine - XML to Moose objects and back
Samba is an Open Source/Free Software suite that provides file and print services to all manner of SMB/CIFS clients, including the numerous versions of Microsoft Windows operating systems.
jQuery plugin providing a widget for date entry and validation. Unlike a 'date picker' the widget is well suited to keyboard-only data entry tasks.
Ansible is a radically simple configuration management, deployment, and ad-hoc task execution tool. It supports a wide variety of distributions, requires no software installed on managed machines, and users can get going in minutes. Extension modules can be written in any language.
Catmandu modules for working with MARC data
The project aims to become the infrastructure to collect measurements within OpenStack so that no two agents would need to be written to collect the same data. It's primary targets are monitoring and metering, but the framework should be easily expandable to collect for other needs. To that effect, Ceilometer should be able to share collected data with a variety of consumers.
Debian is a free operating system (OS) for your computer. An operating system is the set of basic programs and utilities that make your computer run. Debian uses the Linux and kFreeBSD kernels (the core of operating systems), but most of the basic OS tools come from the GNU project; hence the names GNU/Linux and GNU/kFreeBSD.