Mozilla's Firefox 3 Beta 1 has been released. The announcment from Mozilla Developer News:

Firefox 3 Beta 1 is now available for download.
This is the ninth developer milestone focused on testing the core
functionality provided by many new features and changes to the platform
scheduled for Firefox 3. Ongoing planning for Firefox 3 can be followed
at the Firefox 3 Planning Center, as well as in mozilla.dev.planning and on irc.mozilla.org in #granparadiso.

New features and changes in this milestone that require feedback include:

• Improved security features such as: better presentation of website
  identity and security, malware protection, stricter SSL error pages,
  anti-virus integration in the download manager, and version checking
  for insecure plugins.
• Improved ease of use through: better password management, easier
  add-on installation, new download manager with resumable downloading,
  full page zoom, animated tab strip, and better integration with Windows
  Vista and Mac OS X.
• Richer personalization through: one-click bookmarking, smart search
  bookmark folders, direct typing in location bar searches your history
  and bookmarks for URLs and page titles, ability to register web
  applications as protocol handlers, and better customization of download
  actions for file types.
• Improved platform features such as: new graphics and font rendering
  architecture, major changes to the HTML rendering engine to provide
  better CSS, float-, and table layout support, native web page form
  controls, colour profile management, and offline application support.
• Performance improvements such as: better data reliability for user
  profiles, architectural improvements to speed up page rendering, over
  300 memory leak fixes, and a new XPCOM cycle collector to reduce entire
  classes of leaks.

Please note, this beta version of Firefox 3 does not contain the new graphical user interface that we talked about recently. Also, Stephan Shankland has a good blog post on Firefox 3 at CNET that is is worth a read.