WordPress has released version 3.3. Dubbed “Sonny” after jazz saxophonist Sonny Stitt, WordPress 3.3 packs in a number of worthwhile upgrades, including a new responsive design that adapts the WordPress admin to smaller screens.

To get the latest version head over to the WordPress downloads page. If you’re already using WordPress you can update from the WordPress dashboard (naturally we suggest backing up your files and database before you upgrade).

Among the changes that make WordPress 3.3 well worth the upgrade is the new responsive admin design. While there are mobile apps from managing your WordPress site on the go, the actual web admin has never adapted to small screens. That changes with WordPress 3.3 and its new responsive admin page, which reflows content to fit the screen you’re using.

Responsive design — that is, using liquid layouts and scaling media to fit any screen size — is moving into the mainstream in a hurry. The past year has seen several high-profile websites relaunched with responsive designs, but WordPress 3.3 is likely the most widely used site yet to embrace responsive design.

Other changes in WordPress 3.3 include a slicker sidebar with “flyout” submenus which put everything in the admin site just a single click away. There’s also a new drag-and-drop uploader, which means you can drag and drop images from your desktop right into the media upload box in the admin (provided you’re using a browser that supports HTML5’s drag-and-drop API). Behind the scenes WordPress is using Plupload to handle the drag-and-drop features. In browsers that support it Plupload will use HTML5; for older browsers it falls back to Flash.

Anyone working on a site with numerous writers and editors will be happy to know that this release features much improved co-editing support. If you’ve ever seen messages like “Warning: [username] is currently editing this post,” you’ll be happy to know that it will now only appear when someone isactively editing a post. Previously the message would often appear even if your co-writer simply left the window or tab open in their browser.

For a complete list of changes and new features in WordPress 3.3, see the release notes.