WordBreaker by Erik Michaels-Ober
WordBreaker is an online version of Jotto, where you play against the
computer. Anagrams count as guessing the secret word, making the game more
about logic and deduction than luck. It supports between three and nine
letters per word, which allows you to control the difficulty of the game
while expanding your vocabulary.
Note that the code is GPL'd and therefore the source is available for download.