WordPress 3.0, the thirteenth major release of WordPress is now out.
Major new features in this release include a sexy new default theme called Twenty Ten. Theme developers have new APIs that allow them to easily implement custom backgrounds, headers, shortlinks, menus (no more file editing), post types, and taxonomies. (Twenty Ten theme shows all of that off.)
Developers and network admins will appreciate the long-awaited merge of MU and WordPress, creating the new multi-site functionality which makes it possible to run one blog or ten million from the same installation.
WordPress 3.0 "Thelonious"