1. Build a WordPress 2.8 Widget with New Widget API – WPEngineer
http://wpengineer.com/wordpress-built-a-widget/
WPEngineer Michael Preuss walks you through the new simpler Widget API in WordPress 2.8 to create a simple widget. Very simple and easy to understand tutorial.

2. The Complete Guide To Creating Widgets in WordPress2.8 – Justin Tadlock
http://justintadlock.com/archives/2009/05/26/the-complete-guide-to-creating-widgets-in-wordpress-28
This is another great resource to learn how to build a widget using the new Widget API by Justin Tadlock.

3. Tutorial on WordPress 2.8 Widget API – Jesse Altman
http://jessealtman.com/2009/06/08/tutorial-wordpress-28-widget-api/
Another easy to understand hello world tutorial on working with new WordPress widget API.

4. Custom Taxonomies in WordPress 2.8 – Justin Tadlock
http://justintadlock.com/archives/2009/05/06/custom-taxonomies-in-wordpress-28
If you find categories and tags too restricting for the stuff you write, Justin Tadlock explains how to define your own taxonomies in WordPress 2.8 to label your posts in the way you want.

5. WordPress 2.8 and body_class() function – Nathan Rice
http://www.nathanrice.net/blog/wordpress-2-8-and-the-body_class-function/
WordPress 2.8 supports location-specific classes for body tag with which you can control the looks of almost everything with just CSS.

6. Load JavaScript Files in Footer of Your Theme – Lester Chan
http://lesterchan.net/wordpress/2009/01/26/loading-javascript-in-footer-in-wordpress-28/
Now you can make your WordPress blog faster by loading JavaScript files in the footer. Lester Chan explains how to do that in WordPress 2.8

7. Displaying Author Meta Information in WordPress 2.8 – Zach Dunn
http://buildinternet.com/2009/06/displaying-author-meta-information-in-wordpress-2-8/
WordPress 2.8 include two new functions the_author_meta() and get_the_author_meta() to display information about authors. Zach Dunn explains how to use these new functions in your WordPress theme.

8. the_author_meta() in WordPress Codex
http://codex.wordpress.org/Template_Tags/the_author_meta
The WordPress codex explains the new author meta information methods, its parameters and examples.

9. Handling Plugin Options in WordPress 2.8 – PlanetOzh
http://planetozh.com/blog/2009/05/handling-plugins-options-in-wordpress-28-with-register_setting/
WordPress 2.8 includes interesting register_setting() function that lets plugin authors leave the dirty stuff to WordPress and concentrate on the functionality of plugin.

10 WordPress Proxy Support – WP Engineer
http://wpengineer.com/wordpress-proxysupport/
If you are using WordPress on your local network which is behind a proxy, then now you can easily fetch content from other websites or RSS feeds as WordPress 2.8 requires just a little edition to wp-config.php to work behind a proxy.

If you know of some other nice tutorials on WordPress 2.8, feel free to share them with us.