Firefox Sync allows accessing your open tabs, bookmarks, history, passwords and preferences everywhere.

UnMHT adds MHT file reading/writing support to Firefox and SeaMonkey.

Add to Search Bar lets you add the search functionality of any page to the search box with no effort.

Gmelius is a free browser extension available for Google Chrome, Mozilla Firefox and Opera that customizes the look and feel.

Memotoo sync all your contacts from Gmail, Facebook, phone, Thunderbird, Outlook, etc in a single address book.