Mozilla developers have quietly launched the first release candidate for Firefox 3.5 today. Like previous releases, it is based on version 1.9.1 of the Gecko layout engine and includes several performance and stability improvements to the new TraceMonkey JavaScript engine. New features like Location Aware Browsing and Private Browsing Mode are part of this version, which also adds support for HTML5 video and audio elements, downloadable fonts, several new CSS properties and HTML5 offline data storage for online applications.
Currently, Firefox 3.5 RC1 is being pushed to beta and preview users through the browser's automatic update function - those using the stable version can find a download link here and avoid the extra steps (official page still links to 3.5b4). This is still pre-release software, so a few compatibility problems with add-ons and websites are to be expected. That said, Firefox 3.5 RC1 should be nearly identical to the final release, which Mozilla says is due around the end of the month. More details can be found in the release notes.