Wprecipes.com has a huge collection of wordpress tips and is updated frequently. It gives a lot of advice to help you customize and hack your existing theme to its full potential.
Themeshaper.com is a great resource for everything about WordPress Themes. They have a great collection of themes to download, and offer great advice on crating your own WordPress theme.
With the Tutsplus Network, they have a section dedicated to WordPress Tutorials. As always, Envato and the Tutplus.com network always offer innovative and unique tutorials that will make it easy to make your WordPress blog that much better.
Problogdesign is your destination for the best tips on writing the best articles for your blog, and optimizing your blog with SEO implementations. They have a whole category dedicated to WordPress articles.
Hongkiat offers a lot of WordPress tutorial articles, and showcases many amazing wordpress themes to download.
Lorelle.wordpress.com has an archives of thousands of insightful blogging tips on WordPress. Although not updated frequently, this is still great source of information on WordPress tutorials.
Wp-tutorials.org, as implied by the name is an rss aggregator on the latest wordpress tutorials and tips from various blogs.
Themelab is a great wordpress design blog, that offers its premium wordpress themes, and also has a tutorial section that will definitely be informational and helpful to readers.
This is WordPress’ official site, which offers wordpress tutorials in a video format, for those who like viewing than reading info.
Wpdesigner.com is a great resource for those who want to design their own WordPress theme. Here is an example of one of their most helpful posts for me when I wanted to experience designing my own WordPress theme.
Webdesignwall.com is primarily a blog about webdesign, but they also have a useful area about WordPress.
Speckyboy is a design magazine that has a section dedicated to WordPress also. Some of the tutorials are very useful in finding a great wordpress theme.
Digwp is an active blog dedicated to wordpress, and created by Chris Coyier and Jeff Starr really give some great tips on customizing your blog.
Bloggingpro is your site to find useful articles on blogging effectively, with tips to help communicate your message more effectively.
Instanshift is another huge and active blog that has a section with great articles on WordPress.
SmashingMagazine is one of my favorite place to find quality themes , and also checking out their Smashing Netowrk on the latest WordPress articles they have to offer.
Noupe shows us unique ways to take full advantage of the robust WordPress platform, with articles showing us how to fully utilize WordPress more as a CMS then a blogging platform.
WpEngineer is a developer’s resource with WordPress Tutorials that help Theme Develops and coders to implement more features into their themes. This is a whole blog dedicated to WordPress, not just a section, so you can be sure to find articles that will help you on everything for adding a metabox, to optimizing your coding.
That is it for today, and I hope you found that these WordPress tutorial blogs were helpful to you, by finding a new theme, finding a way to hack your own, or finally taking that extra step to develop your first WordPress plugin or Theme.