I've recently been using the Google translate utility to translate between Norwegian and English. All you have to do is type or copy and past in the box, select the proper languages from the list boxes below and press Translate. It's not perfect, but it's free and is the best of the various options I've tried for large translation duties.
For individual words, I use online dictionaries from iFinger. It provides a rich set of definitions for each word as well as contextual usage.
If you have an iPhone, there are several translation applications that do a pretty good job, some of them even attempting pronouncing the words with a machine voice. Search for Norwegian in the App Store.
Note that all of these are for the most common Norwegian language, bokmål. They do not translate nynorsk, which is used by a minority of Norwegians; Norway's many rural dialects; nor do they translate the old Danish-Norwegian (dansk-norsk) in which many church and tax records were kept before the 20th century.