I've recently been using GasORM which is a very neat little Object Relational Mapping (ORM) library for CodeIgniter 2.0+. I wanted to help out a little bit with this great library so I have written a little tutorial
This example application is now included as part of the Gas ORM documentation. It can be found at http://gasorm-doc.taufanaditya.com/example.html . If you are looking for a very simple, efficient and lightweight library for database interaction then check out GasORM.