The ArraySource is a read-only datasource for CakePHP's ORM which uses an array of records inside the Model classes. It was originally created by Juan Basso a couple of years ago. Since then it has been moved to the official CakePHP Datasources plugin and is compatible up to version 2.4.
It is pretty useful for things like statuses, genders or countries for example. These things are usually static and therefor ideal to move out of the database. Using the ArraySource you would still be able to use them in associations and they will be merged in when you do a find. It works with Containable as well. So it's a good replacement for ENUMs, which aren't supported by CakePHP.