The editor of TranslateIt just opened a website with free additional dictionaries for its program. The dictionaries are available on http://www.mytranslateit.com. The site contains of about 70 dictionaries with almost 5 million entries. Users can download from the site English, German, Russian, Spain, French, Italian and Czech dictionaries.
TranslateIt! for Mac (http://www.mac.gettranslateit.com) is a multilingual dictionary that allows you to look up words on the fly on your Mac.