The web page http://freshgroovy.com/groovy/ provides a PPA based Ubuntu package repository. The packages there are updated on a regular base, but not 100% in sync with our releases. New packages are announced on twitter at @FreshGroovy. For instructions on how to use the repository, please visit the website.
Other ways to get Groovy
You can use the Groovy Enviroment Management Tool if you want to maintain and switch easily between different versions of Groovy.
If you're on MacOS and have Homebrew installed, you can run "brew install groovy" to install Groovy.
If you're on MacOS and have MacPorts installed, you can run "sudo port install groovy" to install the latest Groovy release.