While it's nice to dominate a major geographical locale, some of the little townships, villages and located-near-the-big-rock-by-the-pine-tree spots in the search engines are ripe for the picking. Professional practices, big-ticket sellers and the like can be located in out-of-the-way places, but still benefit from targeted local promotion.
This is especially true for one-industry towns. For example, Saugerties, NY is a major hub for antique dealers in the North-East USA. The town itself is about 1/2 of a block of businesses, but there are a bunch of antique dealers, used book sellers, etc., in that location and the surrounding area.
If you're thinking in terms of getting the right businesses to promote in your area, look at the ones that have one or two ZIP codes (for those of you in the US) or postal codes and a big ad budget. It may take some digging, but they are there. These folks need help -- and you can give it to them!