Google weighs less value on most directories, but there are still some that really help improve Page Rank like JoeAnt, DMOZ, BestOfTheWeb.com, the Yahoo Directory, and Business.com. I suggest finding 10 really good high PR and well known directories and setting a simple $1000 budget to get listed on those directories. The longer your listing lives in the directories, the higher your PR will go.
When it comes to traffic, you won't get much traffic from the directories, and even if you do, it's doubtful that the traffic will convert. Instead, you'll get the traffic from your improved Page Rank because that will improve your search ranking.
Hope this helped!
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