It's like a copy writer's (or author's) best friend! IsThisAWord.com is exactly what it sounds like. A simple site where you can type in any combination of letters to see...well, if it's a word.
If it is, it'll give you the definition. If not, well, now you're free to go forth and trademark your shiny new word.
It's not just for Scrabble players and dictionary-haters. I could see how this could be helpful to SFF writers who commonly make up words and names for their worlds. I typed in "Gryffindor" and IsThisAWord said, "YES. But it's a proper noun, so whatever."
Gotta love a website with a personality.