I'd like to point out a flaw in simple ajax shoutbox. WordPress automatically searches for wp-config one folder above the wordpress root, allowing you to move the configuration file outside the www root, for example. It's somewhat of a security feature.
Unfortunately, the shoutbox only searches for wp-config.php in the wordpress root so when you move it one folder up, it breaks. Simply adding a "../" to the path stored in ajax_shoutbox_process.php doesn't solve this issue.