The WPFirstAid Sample Plugin is a simple plugin designed as a tool to learn from or, in some cases, to build new plugins with. Its real world usefulness is essentially non-existent but it does serve the purpose of showing working code that help sort out the requirements to create a plugin that is widget ready. … ∞
A list of WordPress version 3.0 Navigation Menu default widget, and wp_nav_menu() function, generated CSS style elements.
WordPress’ calendar default widget having issues displaying months correctly. See this ticket at trac: #11414