Babylon is a complete dictionary and translation solution, perfect for anyone who frequently works with multiple languages.
Babylon works from various aspects. The main interface is a translation window. From here you can access all the program features, as well as the configuration options. There is also a floating module which will appear when you ask Babylon for a translation. The whole module can be disabled if you want.
No matter which option you use, Babylon provides access to a standard multi-lingual dictionary (to which you can add an unlimited number of additional dictionaries), a text/document translation feature, a unit converter, web search and, of course, access to Babylon's paid translation services.
You can also use Babylon inside applications and online as an on-the-spot translation tool. You can configure the feature in the options area, but the default hotkey is Ctrl+right click. This will allow you to translate whatever word you happen to be hovering over or have highlighted.
In all, Babylon is a very complete tool for language enthusiasts. The translations are accurate (in the context of machine translation) and system-wide integration means that you'll never have to wonder about a word again, no matter what you are working on.
If you have to work with foreign languages on a regular basis, Babylon is a comprehensive, well-integrated tool for the job.