Gearman-and-Kohana-example-project is a project mainly written in PHP, it's free.
This is a sample Kohana 2.3.4 project that shows the differences in speed in using Gearman / not for sending emails via SMTP, it was written for a presentaion at Kohana PHP Conference London 2010.
This is a sample project using Gearmand, Gearman PHP extension from PECL and Kohana 2.3.4 to show the speed increases possible for the front end user interface when sending emails.
You will need to update the application/config/email.php with a valid SMTP host / user / password / etc.
If your gearmand is running on a different port and server you will need to alter this in application/config/gearman.php
You will also need to compile the gearman server & PHP module for it. Please see the presentation on my Blog. To run the worker, open a shell and change to the folder with the code in and execute;
php index.php "gearman/workers"