It's always nice to learn something new. I decidet to start tiny ERP system with Fuel PHP as RPC backend and evntualy extjs 4 as a frontend. The project is located on github: malko-erp.
My first try today is wih the RPC controller (controller/rpc/product.php) and actually creating a working model (model/product.php) from scratch.
I know there is an ORM class, but I preffer more "Active Record"-ish approach.
I'm using PDO for the connection because my choice of database is PostgreSQL and Fuel still lacks native Postgre support.
