I see Charles and I were typing at the same time in our previous posts but he typed faster.
Charles,(Franglais), has more knowledge than I, but I do disagree a bit on his choice of filters.
I'm convinced that a clear or uv filter to protect the lens is almost useless and will only add another piece of glass between your subject and your sensor. It will not add to the quality of the pic and may degrade it. This is a subject of debate amongst photographers so you must decide yourself. The lens hood which comes with almost all Nikon lenses is more protection than you'll need unless you are shooting in windy, dusty conditions.
However, you WILL need a circular polarizing filter, the effect of which cannot be done in post editing. Here is one article with some sample photos: http://www.offrench.net/photos/artic...ing_filter.php
Good filters cost money. The brands I know that make good ones are B+H,(not B&H), Helipoan, and the higher end Hoyas. Before I got advice here, I bought 3 for different lenses at 70 to over a hundred. Now I know that you will only need one. Get the biggest one you think you'll ever need,(think ahead to what you think your biggest lens diameter will be in the future), and get the best one you can. You can then use that filter on all of your lenses by getting adapter rings. The other way to go is with Cokin filters and filter holders. The Cokin filter holder is a device that attaches to your lens and hold filters. No screwing them in and holds many sizes to fit many lenses.
I shoot with a D80 that uses the same battery and have never run out of juice with a full charge, shooting maybe a couple hundred a day. If you are going to take thousands of photos a day you may want a battery grip. Or you can just carry a spare battery. I guess they help with holding the camera steady but I've never used one so don't know.
The sb600 flash, Charles recommended is a good one. The sb800 is better. The sb900 is the newest but I've heard differing opinions on it.
Research, research, and then research some more. Google or Bing will bring you more info than you can read in a life time. And you can always ask here.
Be sure to post some pics when you do get the camera and you'll get friendly pointers on what you're doing right or wrong or just how to make them better.
Welcome to the passion!