On the Zend Developer Zone today, there's a new post about a new project that's been launched - an object persistence layer for PHP, Junction.
The goal is to automate basic query construction, decouple the application from the database, and allow for faster development. With Junction you write a simple data object (the only requirement is that it have getters and setters) and a mapping file, following that you can start interacting with the database.
The project is completely open source (under the MIT license) and is operating under the "release early, release often" mentality. You can grab this most recent download directly from their site.