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.
A collection of useful grid field components.
Silverstripe 3 Newsmodule
A decorator for a form field that manages as has_one relation, to allow adding a new object on the fly
An extension that adds a star rating system + UI to any DataObject type
A silverstripe form field based on http://ivaynberg.github.com/select2/
A SilverStripe module for creating templates within the CMS that can override those defined in the theme, for both Layout and main templates
Faster, easier client and server-side form validation for SilverStripe
simple chaining hash table implementation written in pure C (c99)
Kernel for I9300