Get a Sneak Peek of Firefox 6
This early version of Firefox 6 introduces a Data Management Window as an experimental feature that provides control over the access that specific websites have to your browsing data, including cookies, passwords, and location information. In the Aurora build, you access this feature by typing "about:permissions" (no quotes) in the Awesome Bar.
There's also a revamped Add-ons Manager with Plugin Check to quickly verify compatibility of installed plugins, and if you use Panorama to group tabs, Firefox 6 purportedly offers faster startup times by "allowing power Panorama uses to load saved tab groups only when using Panorama."
Firefox 6 in Aurora form also boasts improved support for HTML5, DOM level 3, server sent events, networking technologies, and other tools designed to make a developer's like easy when building advanced web apps.
You can download Firefox 6 from here.