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.
Moodle (lang) (http://docs.moodle.org/en/Translation)
Moodle is translated into over 70 languages by a dedicated corps of worldwide volunteers. Translation has actually been going on a lot longer than the stats here may suggest, because the language packs used to be part of the main Moodle code base.
Mozilla Central (only)
https://www.openhub.net/p/firefox includes old cvs repos. I made this project to check mozilla-central repo only.
an NCIP server, from the Evergreen ILS project http://evergreen-ils.org
Perl5/Moose wrapper for Net::SSLeay (OpenSSL SSL library bindings)
Perl module Net::AS2 implementing AS2 file transfer protocol
Neuros Database Manipulator (http://sourceforge.net/projects/neurosdbm)
Neuros Database Manipulator - Browse and modify the database of your Neuros Audio Computer. Neuros Database Manipulator is written in Java for cross platform support.
OLPC DS-Backup (http://dev.laptop.org/git?p=users/martin/ds-backup.git;a=summary)
Part of the OLPC infrastructure - these are the XO-to-XS backup scripts.