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.

Apertium is a free/open-source rule-based machine translation platform.