ObjectGraph Dictionary is an online dictionary that uses a similar technology to GoogleÃ¢â‚¬â„¢s Suggest.
“Ho hum” I hear you say, “another dictionary…what else you got”.
No seriously this is really impressive, not only will it try and suggest the word you are typing, it also throws up a definition for all the suggested words, and it does it as you type (like the guess ahead that I keep turning off on my PocketPC but that’s another bleat for another day). This is just so cool if you looking for a word and not quite sure if it means what you think in means (Inconceivable… :-)), just start guessing and checking the suggested spellings and definitions.
I give it 10 minutes until Google snaffles this idea and probably 15 until Micro$scum do.
Update: OneLook’s reverse dictionary lets you describe a concept and get back a list of words and phrases related to that concept. Your description can be a few words, a sentence, a question, or even just a single word then hit the “Find words” button. (Keep it short to get the best results.) In most cases you’ll get back a list of related terms with the best matches shown first.