Welcome aBoard Silen!
to find out every word that ends in "ation" or "ate", etc

I thought at first that a "suffix" dictionary would almost certainly not exist. After all, how could it be useful? But then it occurred to me that maybe you're looking to find rhymes.
If so, a quick google found a rhyming dictionary at:
http://www.rhymezone.com/

If it's not rhymes you're after, I'd be fascinated to know of other uses for a "suffix dictionary"!

Fisk