The well-known Mac program Crossword Assistant comes to the iPhone and iPad. Here is an easy-to-use helper for players and creators of crosswords and word games: quickly find words and phrases when you only know some of the letters, and solve complete or partial anagrams.
CAiOS has a comprehensive and tested English dictionary of 326322 words and 1658950 phrases, and also dictionaries for Italian, French, German, Spanish and Dutch. You can look up word meanings in all 6 languages. You can freely download a number of others, including Shakespeare, the Bible, Reverse English, Cities and Rivers. You can even add your own dictionaries!