WordPress 2.5 was released over the weekend. It was the culmination of six months of work by the WordPress community.
The latest version offers a cleaner, faster, less cluttered dashboard, dashboard widgets, multi-file uploading with progress bar, one-click plugin upgrades, built-in galleries, salted passwords with strength meter, cookie encryption, media library, concurrent post editing protection, search posts and pages
You can read about an overview of the features with screenshots or view a 4-minute screencast of the new interface.
You can also jump straight to the upgrade and download information.