I adapted a Javascript & AJAX tutorial off of sitepoint to work with CodeIgniter. It uses jQuery to the handiwork. It is a simple AJAX chat script, not the most advanced thing in the world. Hopefully it will get better in the future.

Here is it in action:

Download jQuery Chat

REQUIREMENTS

1. You have Downloaded and Installed codeigniter.
2. You may want to check for a new version of jQuery.The version of jQuery that is included is 1.2.1. You can find the current version of jQuery here.
3. The root folder is where codeigniter is installed.
4. You are using MySQL.

INSTRUCTIONS

1. Open /system/application/config/autoload.php
   Verify that you are autoloading the database library. You should see ‘database’ listed in the $autoload['libraries'] array.
2. Open /system/application/config/database.php
   Verify that you have the correct information for your database.
3. Upload /system/application/controllers/chat.php
   to the corresponding folder on your server.
4. Upload /system/application/views/chatty.php
   to the corresponding folder on your server.
5. Upload /public/js/jquery.js
   to the corresponding folder on your server.
6. Upload /public/images/blueloading.gif
   to the corresponding folder on your server.
7. Run the sql.sql file on your server using a tool like phpMyAdmin.
8. Open a web browser and goto http://yourdomain.com/chat or http://yourdomain.com/index.php/chat if you have not configured your htaccess file.