On PHPBuilder.com today there's a new tutorial walking you through the creation of a simple WordPress plugin that shows the latest YouTube video from your blog's channel.
Think of plugins as components where you put your functionality and widgets as components of your user interface. Building your own WordPress plugins and widgets will make your blog truly original, and all you need is basic PHP and HTML knowledge - and your imagination.
They help you get started with defining a few constants, registering the actions with WordPress, building the widget (with complete cut-and-paste-able code) and including it in your WordPress blog. You can download the complete source if you want to get started quickly.