On NETTUTS.com there's a recent tutorial - the ninth part of the "CodeIgniter from Scratch" series - posted (by Burak Guzel) for all of the users of this popular framework out there. It looks at, starting from the very beginning, how to create an upload and image manipulation script for use in the framework.
In lesson nine of our CodeIgniter series, we'll build a small image gallery that allows you to upload files, and automatically create thumbnails
He links to the previous eight parts of the series if you need to catch up as well as the source code for this installment so you can follow along with the screencast. For those more on the go, you can also download the screencast and watch it whenever.