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.
Docvert is a web application which takes word processor files (typically .doc) and converts them to OpenDocument and clean HTML. The resulting OpenDocument is then optionally converted to HTML or any XML. This is done with XML Pipelines, an approach that supports XSLT, breaking up content over headings or sections, and saving those results to multiple files (e.g., chapter1.html, chapter2.html, ...). The result is returned in a .zip file. Docvert has a user-friendly interface, and it's easy to integrate with other software as it uses a simple REST-style interface. The XML produced is easier to understand and more structured than the WordML or .DOC formats.
Domain Name Registry System (http://sf.net/projects/dnrs)
The Shared Registry System is software (client and servers) for managing a domain name registry, and is most likely to be of use for managing a country TLD. The software was originally developed in 2002 to manage the New Zealand (.nz) domain name space.
A database designed for the typical Web usage patterns for a database. It is being designed for massive concurrency on modern multi-cpu/core architecture. The code is originally derived from MySQL.
Drupal (core) (https://www.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 Drupal's core, you can find the contributed modules page at http://ohloh.net/projects/3502.
The Drupal Console is a command line interface tool, to generate boilerplate code and interact with a Drupal 8 installation.
PHP library to embed any web service or page (oembed, opengraph, etc)
Perl CPAN module for fixing up data which contains mixed encodings (ASCII / UTF-8 / latin-1 / CP1252) and outputs clean UTF-8
CPAN module: C/XS implementation of Encoding::FixLatin
Epiphany extensions (http://www.gnome.org/projects/epiphany/extensions)
Epiphany Extensions is a collection of extensions for Epiphany, the GNOME web browser.
Evolution provides integrated mail, addressbook and calendaring functionality to users of freedesktop.org compliant desktop environments.