I came across this yesterday and thought I would share:
http://www.filmsite.org/bestspeeches.html
It’s an inventory from Greatest Films of the Best 700 Film Speeches and Monologues, indexed by year. I CANNOT guarantee that these monologues are doing what I want them to do (strong thematic coherence/central idea) but it’s a great place to start your search. The older you go, the more likely you are to find something of higher quality and that will be unique among your peers.
L