Amazon's Simple Storrage Service is a great service for storing lots of files on a solid and stable system. I have been experimenting with it for a few days and quickly found the need for a CodeIgniter library to upload files to S3. Amazon provides us with a great PHP SDK source but because it uses some PEAR packages I went looking for a version that implements the REST interface without the need of those packages.
I found a standalone version that uses cURL released by undesigned and modified the constructor so that it supports CodeIgniter's initialisation with a config file. You can find the modified file here
All the methods remain unchanged so you can still use the original documentation.