I've been trying to decide. I have a long list of ideas that I never get around to. Maybe I'll list the likely options and anyone who wants to can weigh in.

Metaethics- in particular a defense of a tolerant pluralism with regard to normative theories, perhaps an explanation/investigation into the is/ought distinction

Quantum mechanics- probably not what I'll do this week because it requires more research than other ideas, but I think we're overconfident in the Many World's interpretation and focusing on the wrong alternatives.

A summary/explanation of Quinean metaphysics and epistemology

The type-token distinction/ambiguity, perhaps going into it's relation to personal identity

An investigation into how mental concepts relate to complexity, by way of refuting Swinburne's Bayesian argument for theism

An explanation of the Dutch Book argument

Thats just the top of my list. As you may be able to tell from the way I've won my karma, I'm quite good with quick and dirty ideas but far less successful with post-length explanations. Hopefully I can get through a lot of these (and hopefully they actually end up being things people want to read).