WordPress 3.0 has just arrived on the scene — the thirteenth major release of the popular blogging software. It’s the result of six months of work from a total of 218 different contributors. You can download it now or upgrade from within your WordPress dashboard.

What’s new in 3.0? One of the best ways to find out is to try out the new Twenty Ten theme, which shows off many of the release’s (which is also called “Thelonius”) major new features, including custom backgrounds, headers, shortlinks, menus, post types and taxonomies.

Thelonius also features a lighter interface, more contextual help options, a boatload of bug fixes, bulk updates and much more. To learn more details about five of the most important updates, check out this brief and informative guide. This video from the WordPress team also explains some of the new features:

For those of you laboring on the backend, including developers and sysadmins, you might appreciate that MU and WordPress have finally merged. Now you’ll be able to run one or multiple blogs from the same installation.

Interestingly, the staff of WordPress/Automattic won’t immediately rush off to start work on WordPress 3.1. Founder Matt Mullenweg said his team will be taking some time to focus on things other than the core product.

“Over the next three months,” he wrote this morning, “we’re going to split into ninja/pirate teams focused on different areas of the around-WordPress experience, including the showcase, Codex, forums, profiles, update and compatibility APIs, theme directory, plugin directory, mailing lists, core plugins, wordcamp.org… the possibilities are endless… We think this investment of time will give us a much stronger infrastructure to grow WordPress.org for the many tens of millions of users that will join us during the 3.X release cycle.”

Are you excited to use the new WordPress 3.0?