I'm in the market for..

So I'm looking to purchase an ND filter. I keep reading photography articles and blogs. Each time I like one of the techniques I read about, or how a picture has turned out, they've used an ND filter. So I will probably purchase one in the coming days, not sure I can wait until my birthday in October. Here are some examples of what I am talking about. They use the ND filter for great sky shots.