Ruby on Rails plugin to allow one application to support multiple independently branded sites github.com/jystewart/theme_support
As we've mentioned in the descriptions of both Generous and Catapult Magazine, we have a few projects that require one application (a single database, consistent tools and logic) to support multiple independently branded sites. For Generous that means allowing partner organisations to have their own communal action-based sites; for Catapult that means multiple magazines being able to make use of the same Content Management System.
Both of those applications are written using the Ruby on Rails framework, a popular open source toolkit. Rails supports "plugins" to provide extra functionality and for some years there's been a plugin to provide the kind of 'theme' support these projects needed: theme_support.
When we started on the Generous project, theme_support had fallen out of repair and wasn't keeping up with changes to the Rails framework. We took it, reworked it, polished it, and James Stewart wrote about the process in some detail on his blog as it helped document a number of the changes in recent versions of Rails. Since then, several other users have contributed changes and suggestions, and we've integrated those to produce the most up to date version of the plugin out there.