Foxmarks
If you use more than one computer then Foxmarks might become handy as it keeps your bookmarks and passwords (optionally) synchronized.
Adblock Plus
This is a must-have add-on for Firefox. Many sites have annoying flash ads in them. Not anymore – Adblock plus blocks them all!
Sxipper
Tired of filling in various web forms and all the spam you get on your e-mail? This add-on automatically fills in registration forms and creates fake e-mails which forward to your e-mail. If you get too much spam from one of the fake e-mail you …