http://www.google.com/tools/firefox/browsersync/

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.

Very cool. Don't know if there's already an extension that does this, but I trust google, and definitely will use this. Especially since I have 3 desktops at home, a laptop, and a computer at work all running firefox...

Seamonkey has had this feature since Mozilla 1.8a5 (which was eventually released as Seamonkey 1.0) that uploads to ftp or http (webdav?). I wonder if the Google code is based off this, and also what license it's distributed under, since I'd love a version that doesn't require a google account.

The remote storage of saved passwords and cookies is a bit worrisome.

Bookmarks are one thing (I use Foxmarks for that), but passwords.... hmmm.