Google Browser Sync

Sync your Firefox across multiple computers.
http://www.google.com/tools/firefox/browsersync/

Gmail This Page Bookmark

This code in a bookmark will create a Gmail compose window with the address of the current website in the text of the email.

You can grab this link and drag it to your bookmarks!
Gmail This

I also modified the "to=" to match my Mail-To-Blogger email address so can blog from a page with the click on a bookmark.

Multiple Firefox Profiles

You gotta try this.
Make a shortcut on your desktop for...
"C:\Program Files\Mozilla Firefox\firefox.exe" --profilemanager
(close firefox and open it using the shortcut)
Add a couple profiles. (ie searching, torrent, email, email02)
Then make a shortcut on your desktop for each profile...
"C:\Program Files\Mozilla Firefox\firefox.exe" -p email02 -no-remote

Way cool!