*FoxmarksIf you use more than one computer then Foxmarks might become handy as it keeps your bookmarks and passwords (optionally) synchronized.
*Adblock PlusThis is a must-have add-on for Firefox. Many sites have annoying flash ads in them. Not anymore - Adblock plus blocks them all!
*SxipperTired 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 just cancel forwarding. Simple as that!
*GreasemonkeyIf you want to make your browsing more comfortable then this comes handy as you can use all the user made scripts. The largest script database is at Userscripts.
*FireFTPDon’t want to install an extra program for FTP? Download this add-on and you gain FTP access to servers from your browser.
*CHATZILLAAnother useful add-on with which you can chat on IRC networks and you don’t have to install a separate program!
*URL FixerEver mistyped the end of a address? This fixes all of your mistakes - if you type hidecodesgalore.or
F it automatically corrects it to hidecodesgalore.or
G