As a "starter" bag, I'd say that one should have the basic body, perhaps one step up from the basic zoom lens (i.e., skip the 18-55 starter lens and get something like the 16-85), and a 50mm prime lens (dirt cheap and spectacularly bright). Toss in a flash (the Nikon SB-600 is just fine, although the new SB-900 looks sweet).

In terms of ancillary equipment, I put a UV filter on all my lenses. It's job is to take one on the chin rather than my expensive lens. I also have a cheap aluminum tripod (probably 30 years old) with a brand-new Really Right Stuff quick-release head on it and a matching L-bracket so I can mount my camera quickly on the tripod. (The new see-in-the-dark abilities of a Nikon D3 or D700 remove some, but not all, of the need for a tripod.)

About the only other gizmo that I'd say really matters is having a good camera bag. I have a fairly compact LowePro bag that has enough room for one camera body, one lens attached, one flash, and one or two spare lenses. Easy to open and get the camera out while on the move. I own much more gear than could possibly fit, so I tend to repack based on my needs for the day. This sometimes means I'm at a loss ("damn! I wish I had my macro lens!"), but I can at least carry the thing around without throwing my back out. I'm about to upgrade from my lightweight D70 to a much heavier D700 and correspondingly heavier lenses. It will be an interesting challenge to sort out how I can keep the weight down.