Ultralingua German-English Dictionary is very complete, and easy to use: insert a word in German and the dictionary shows the equivalent in English, or by default will show the nearest thing.
Ultralingua German-English Dictionary also includes an interesting number translator for any number inserted to its English text equivalent. It also has a tool to look for real examples via the browser that is integrated.
Ultralingua German-English Dictionary is also great as it comes equipped with hundreds of colloquial terms and expressions, and you can also look for different verb conjugations.