Lens advice for Nikon D90?

I just bought the Nikon D90 to replace the D80 I currently own. I still have the Nikon 18-55mm II and the 55-200 VR lenses. I was also thinking of getting the Nikon 50mm f/1.8 as I want something that will work great in low llight situations. Is there a better lens I should add to collection? I love landscape photography. I would like to get into macro work as well. I read on Ken Rockwell's site that even the 18-55mm is a good macro lens.

The 18-55 is not a good macro lens. You could use extension tubes to improve the close focus limit somewhat, but it's a far strech from macro either way.

The 50mm/1.8D is a solid choice, the 50mm/1.4D or G would be better. If you get a D version then you can reverse mount it with a reverse ring and use it for macro shots, but that's very tricky to do. A proper macro lens will be much easiert to use there.

For landscape, if the 18mm end of your current lens doesn't do it for you, consider the Nikon 10-24mm, Tokina 11-16mm or Sigma 10-20mm (the cheaper variable aperture one is much better than the more expensive fixed f/3.5 one!)

There's no lens that will do all this in a single package, sorry.

As a owner of a D90 and D80 and D200?(you get the point… ) I will advise you not to settle on the bottom rung, meaning don't buy another 18-55mm (it is a waste of money) The 50mm f1.8 or 35mm f1.8 are both fantastic lenses and very good additions to your lens collection.

For landscapes the 12-24mm f/4 is a great lens and very different than either your 18-55mm II and the 55-200 VR lenses. Another lens I love and own is the 10.5mm fisheye which I use frequently on my D90, very different view…

For macro I use a 55mm micro nikkor (the 60mm or 105mm micros are very good) sadly the 18-55mm isn't really a macro and does terrible at being one.