SitePoint.com: Scheduling Tasks in WordPress: a Plugin Developer's Guide
On SitePoint.com there's a new tutorial posted in their "PHP & MySQL tutorials" section about using a feature of WordPress that some might not know about but can be extremely handy when you need it - using WordPress tasks.
Scheduling the execution of certain functions at a time in the future is a key feature of the WordPress API, having been introduced in WordPress version 2.0. It's also a topic that's poorly understood by many developers, as it's only briefly covered in WordPress's documentation. Apart from facilitating maintenance tasks, scheduling code to be executed in the future opens up a lot of interesting possibilities for plugin developers.
He talks a bit about how the WordPress tasks work (via the wp-cron.php script) and the two types of tasks - one-off and recurring. He includes code and examples of how to set up each and some other handy features like custom timing for tasks, getting the list of scheduled tasks and a few things to watch out for when working with the feature.