Google Translator for Firefox. With this addon you can translate any text to your own language with one click or hot-key. You can either translate the selected text.
It offers tabbed browsing customizable, the standard on all browsers now for quite some time. It also has an integrated search engine and is easily customizable.
From the homepage, you'll have access to a Google search box and a list of shortcuts to access your downloads, bookmarks, history, add-ons, synchronization and settings. It has all the essential features and also includes a spell checker, built-in PDF reader, navigation with geotagging, and much more.