There's a lot of research to do. For quotations, I'm thinking of starting with Gertrude Stein, but then again, I haven't checked to see if any of her work is public domain yet.
Fair Use (FAQ) | U.S. Copyright Office
Even work not in public domain can be used for commentary or research, but a website is a different matter.
So finding someone both current, and not current, in terms of ideas, is the challenge.