Selingua is a vocabulary training program with extensive built-in dictionaries -- more than 2000 words in each of the following languages: English (both American and British), German, Spanish, French and Swedish. The program can be used by native speakers of any of these languages since the user can choose the language of the on-screen instructions.
There are six different exercises for practicing vocabulary and verb inflections, including a crossword exercise. Users can also add their own words to the dictionaries. Selingua is freeware.