Traduisons! (French for "Let's Translate!") is a front-end for Google Translate, allowing translation of words and sentences without opening the browser. It's written in python and gtk or optionally runs from the commandline.
It is confirmed to work in both Linux and Windows. Anyone interested in porting this to a different OS, please feel free to do so. Patches welcome.
Traduisons! is focused on being as streamlined and fast as possible. It's meant to be a quick-reference tool, not a large scale document translator.
Traduisons! is not a translation engine itself. It works by sending input text to web-based translation services and parsing the resulting page to extract the translated text. It is capable of supporting any language recognized by google translate, including "auto detect".
Since almost all of the lag between input and translated output comes from the server, the only factor affecting speed is the amount of time it takes the user to select the correct languages and work with text. All of Traduisons! can be controlled via text commands in the translate box. For those of us who can type it's much faster and less frustrating than point and click dropboxes. See the wiki for usage.