Which Macro Lens?
Often when people are interested in getting into close-up photography, they spend some time trying to figure out what the best macro lens is. After all, they aren't certain how well they will like close-up work, and they can't really afford more than one new lens. I wrote recently about a great inexpensive way to get started with macro by buying two-element close-up diopters for the lenses you already have, but there comes a time when you've just got to have a real macro lens. So which one should it be? Well, it depends on what you want to use it for.
For those people who want to take close-up pictures of stamps, currency or other flat subjects that don't move much, a short focal length such as the 55mm (manual focus) or 60mm (auto focus) Nikkor would work great and is more affordable than longer focal length alternatives. Such a lens though provides very little working distance,. At closest focus with the 60mm micro, your subject would be only about 4 inches from the front of the lens. That's darned close.
Sneaking up on a live butterfly with one of these would be mighty frustrating. Because of this, something with more working distance is needed for nature work,. The minimum acceptable focal length for such subjects would be the 105mm nicro-Nikkor with the 200mm being an even better option. Closest focus with the 200mm is more than double that of the 60mm micro.
Longer focal length macro lenses have another advantage in that they enable you to control the background far better. The angle of view of a 105mm lens is 23 degrees along the diagonal, only 12 degrees with the 200mm macro. This means that with the same framing on your subject, you would see a much narrower slice of background. Simply moving a little bit one way or the other would allow you to completely alter your background by simply looking a different direction. On a shorter focal length lens, your view often includes at least some clutter that can be hard to avoid.
When shooting on digital, my current favorite is the 70-180mm micro-zoom. This gives me the equivalent angle of view of a 105-270mm would have on a film body. It doesn't focus all the way to life size as the other auto-focus Nikon macro options, but the flexibility provided by the zoom has proven quite useful in the field.
Longer focal length macro lenses do tend to cost more though, but it can be a lot easier to get good shots when using one. While I can't tell you which lens best meets your needs, hopefully this at least gives you some information to begin your search with.