I ran across a good set of articles on mastering WordPress.
There are four articles in the series covering tips, tutorials, hacks, themes, plugins and best practices from some of the leading WordPress developers.
Part One: Mastering Your Theme Hacks and Techniques
Part Two: 45+ Must See WordPress themes
Part Three: Powerfull List of WordPress Lifesavers Plugins
Part Four: Elegant and WordPress Designs- Best Practices