You could look for additional dictionaries for use in
Dictionary.app (included with OS X). Just like my Wikipedia dictionary (don't know if it came with the vanilla OS X installation) loads data from the web, so could your translation service. It seems to be not possible to enhance the Cmd-Ctrl-D "quick dictionary" with such a custom dictionary, though.
You can enable debugging/developer mode for Dashboard which allows you to drag widgets out of the "Dashboard view" onto the normal desktop, so you always have the widget visible.
You can look into creating a custom Text service for the Services menu (select a word in the browser and look under
Application -> Services -> Text. In
System Preferences -> Keyboard -> Keyboard Shortcuts -> Services you can even set keyboard shortcuts for such commands.
The custom service can be easily created using
Automator.app, I just tried:
- Create a new Automator document based on the "Service" workflow
- Add a single action:
Run Shell Script with the input passed as arguments, and the command
open http://dict.cc/?s=$1 (or whatever website you use for translating)
- Save as
Translate to German (in my case it's German)
- (Optionally) Assign a keyboard shortcut in
- Use it