The GroovyRunner allows you to run arbitrary Groovy scripts with full acces to the Alfresco Java API in the Alfresco repository. It is a great tool for testing, analysis, maintenance, setup and repair. We have been using it for years and it has become our Alfresco repository "swiss army knife". If you are familiar with the Alfresco Java API, you will feel at home here :) All services are available exactly as they are in the Java API. We have added some helpers to make things easier, but ultimately with access to the full API you will never get stuck.
The documentation and download can be found here.
We have created many scripts over the years. There are simple repair scripts, setup, integration testing, API discovery. Most of them need some explanation at the very least. I'll sift through them over the next few weeks and post them here as I find useful ones.