In this new post from The Bakery there's a tutorial on creating a REST web service with the help of the CakePHP framework:

This is an example used to request the list of countries from you database to share among many applications (I use it to have consistant set of country_id's among a couple of different applications that all share the same database back end: REALBasic Application, Aperture Plug-in and a CakePHP web application)

They provide the code (and settings) you'll need to use to get the REST web service going. They create both a component and a helper to make the process easier and provide a SQL dump for the countries table and the Model, Controller and View templates you'll need.