Google Browser Sync for Firefox is an extension that continuously synchronizes your browser settings – including bookmarks, history, persistent cookies, and saved passwords – across your computers. It also allows you to restore open tabs and windows across different machines and browser sessions.
Google Browser Sync is completely automated. The settings you select at startup are automatically synchronized across each of the computers on which you install Browser Sync. You won't even need to log in every time you start the browser. You can change which browser components are being synced – or even stop the syncing process entirely – using the settings panel in the upper-right corner of the page. The settings panel also gives you access to your PIN.
Looks really good! This will help people try out new versions of Firefox a little more comfortably, since their settings will always be secure with Google (don't roll your eyes!). This is something that I've been looking forward to for a while. You can get it from here