WORDNIK

This from Wordnik-

Wordnik wants to be a place for all the words, and everything known about them.

Traditional dictionaries make you wait until they've found what they consider to be "enough" information about a word before they will show it to you. Wordnik knows you don't want to wait—if you're interested in a word, we're interested too!
Our goal is to show you as much information as possible, just as fast as we can find it, for every word in English, and to give you a place where you can make your own opinions about words known.

By "information," we don't just mean traditional definitions (although we have plenty of those)! This information could be:
An example sentence—even if we've only found one sentence for a word, we'll show it to you. (And we'll show you where the sentence came from, too!

Check out WORDNIK - an amazing site which The Bookman reckons may spell the demise of the dictionary as we know it.

Picture above from the Wordnik blog - Photo by, and licensed from, Gary Simmons.