James Altucher has really had an impact in the last few years with his books, his blogs, his videos, etc. His core ideas are contained in Choose Yourself. I want to encourage you particularly to apply one of them he advocates for exercising your “idea muscle” that I have started calling the Ten List.
The Ten List is part of his four-part system he calls The Daily Practice–or, actually, a technique that addresses the Mental part of the four. So it’s not particularly about speaking or writing, but I have found it to be really useful for both.