xPDO is a light-weight ORB (object-relational bridge) library that works on PHP 5, and takes advantage of the newly adopted standard for database persistence in PHP 5.1+, PDO.
There are a number of benefits to using xPDO instead of writing SQL directly against the database.
In an effort to remove the dependency on Ant, the Java-based build tool we have been using to build, test, and produce distribution packages of MODx Revolution, I spent the last week learning Phing, refactoring the xPDO and MODx Revolution build processes to use it, and writing a custom Phing Task to handle our YUICompressor requirements.
I've restarted work on SQLite support for xPDO, and things are looking good so far. This will be targeted at PHP 5.2's PDO driver for SQLite3, not the older sqlite2 PDO driver included with PHP 5.1.x that is no longer available via PECL. It may be easily adaptable however.