I own a small local website at All About San Luis Obispo. There is an attraction in SLO (what we call that town out here) that is famous worldwide. It is called The Madonna Inn.
For some reason that I can only attribute to my own laziness, I never wrote an article about that incredible hotel. I've had the site up for two years.
So, I wrote a short article next week. As soon as Google picked up the article (really quick if Google likes your blog, hint, hint) I started getting 3-5 additional visitors a day through the search engines. (Hey, Google, I am sure you are awaqre, but some of those searches were from Bing.com).
It made me think, Dang it! If I had the article up on the site two years ago I wouldn't have missed those 2,000 additional visits. My bad, our gain if you act on your keyword shortcomings.
Not that difficult. You can use the Google Keyword Tool or another good keyword tool. The best I've found is Micro Niche Finder. (I AM an affiliate owner who paid full price for this great product)