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.
Simple on the fly caching of dynamic content for Silverstripe
Exclude children of configurable classes from showing up in the sitetree
Module for improving automatic image cropping in SilverStripe 3
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