Recently we decided to move our Turbogears 2 CMS, ACRCMS, from an example of how to use libacr to something more complete. Consequently to this decision we implemented the plugins architecture inside libacr, which permits to add plugins to libacr at run-time.
Until now there were no real plugins, the only available plugins were the three acr slice templates which have been moved from an internal function to a plugin.
Today the first real plugin for ACR has been pushed in a separate branch, the plugin is the Theme engine, which permits to add theme support to ACR. The plugin is available inside the ACRCMS acr_plugins directory and is now loaded by default by ACRCMS, it will be officially part of ACRCMS in the next release.
For now you can test it from the themable branch of ACR