What's the simplest, most brain-dead obvious application of your skills/technology you can think of? Ideally, it should be something you can't believe anyone would pay for.

That's probably your best bet for areas to start investigating. Seriously. Smart people tend to think they have to solve hard problems, but usually (in my experience, and from watching other successful entrepreneurs like Patio11), the money's in doing stuff that you think is really easy, and other people think is hard.