On PHPMaster.com today there's a new tutorial showing how you can create a custom WordPress plugin for the popular PHP-based blogging/CMS tool.
If you’ve ever used WordPress to build a site quickly, chances are you’ve used one of the many plugins that are offered to extend the functionality of this popular blogging software. Plugins are one of the many things that make WordPress so attractive. [...] There are times, however, when you can’t quite find what you need from existing plugins. This article will show you how to create your own WordPress plugins by walking you through an example to display some text using a widget in a the sidebar.
He walks you through all of the steps you'll need to create the plugin - making the main plugin file (definition) and using some of the methods available to create the functionality: update, form, widget and the constructor to set it all up.