entropyembrace wrote:As far as I know no SLR's do, how close you can focus to the camera is determined by which lens you have mounted...so when you're buying lenses check the minimum focal distance. I know the 18-55mm VR lens you can get in a kit with the D90 focuses close enough for macro photography.

This is my impression as well.
True macro lenses can achieve 1:1 magnification, which is to say, for example, that a 1cm long bug will produce a 1cm long image on the digital sensor or film. Some lenses labeled "macro" (or micro, or makro, all the same thing) do not do this, so be sure to check the magnification ratio before you buy one.
Also, 1:1 magnification is not dependent on the focal length of the lens; you can have a 135mm macro lens or a 20mm macro lens (or anything in between), the only thing that changes is the distance you must hold the camera from the object, which then changes the perspective.
Because of the perceived perspective change, wide-angle macro lenses will produce crazy distortion effects and telephoto macro lenses will have an extremely small depth of field (DOF gets smaller with BOTH increased focal length and increased image-to-focal plane distance). A lot of people think the "ideal" macro lens length is approximately normal, as long as you don't need to worry about keeping some distance between you and your subject, as with bugs and such. If this interests you, you may want to check out the
Nikon 55mm f/2.8 AF macro lens. I think it is only available used, but BH, Adorama, or KEH all have reliable used equipment sales. KEH is best, as their condition appraisals are known to be conservative-- I would not hesitate to buy a BGN item from them.
Nikon now makes a 60mm macro lens in two flavors, if you prefer to buy new, but don't get the "G" version! Don't get ANY "G" lens, actually-- for some stupid reason Nikon decided to remove the aperture ring from these lenses.