You can’t go wrong if you decide to build sites/campaigns in any of those markets.
Then once you have a market in mind, the next step is to put together a strong keyword list. Awhile ago, I wrote a post called Highest Volume Keywords by Category, which is about using Google Insights for Search to locate popular keywords by niche. When I wrote that, the Google keyword tool was not returning results when you searched in the same fashion (using no keyword), but today it is.
Side note: On Thanksgiving, when asked was I was thankful for, I said the Google Keyword tool 😀
Check out Aaron’s list here to find markets, then use the category selection on the keyword tool to find the top keywords in that market. Simple.