Google Translate is very handy if you need to roughly translate text or words from an unfamiliar language. Google has beefed up its capabilities when translating individual words, offering up lists showing common reverse translations for particular terms.
Google also shows the relative frequency of given translations and commonly-used synonyms. For commonly-used words which can have several different nuances (such as French grand in the screenshot), the extra information can help you decide if the translation is accurate. None of this can substitute for a thorough knowledge of the target language, but it definitely helps. Right now the extra data is only being offered for translations into English, but Google says extra languages will be added over time.
[Google Translate Blog via Google Operating System]