Dogwood bushes and Rose of Sharon grow rather quickly and make a nice "green screen". They lose some of their coverage in the winter, though, so you way want to mix in a row of evergreens for good measure.
Chamaecyparis lawsoniana 'Columnaris'. Grows quite fast, at the rate of 8 in to 1 ft per year and stays green in the winter. We have a regulation regarding fence height. Whoever wants a higher fence uses this tree, it can grow up to 40 feet.
I can't get past this comment without noting how invasive and aggressive spreading rose of sharon is, I'm constantly pulling out new growth due to my neighbor's plant. What a headache.
