I like writing and would like the public accountability to make me write more often.

I can't think of anything worthwhile to write about.

I would say that those two sentences are in conflict with one another!
If you like to write, who cares if others have already written about the subject? Look at how many tutorials are out there for monads in a functional language...
If you like it, you like it and write about it. The problem may arise if what you like is not writing per se, but you like exclusively the social status that writing gives.