Nikon Lens

Try Nikon's 18-200 Zoom with Vibration Reduction. They're around $700 which is pretty good for a lens that can serve most all purposes and has image stabalization built in. For around $300, you can buy a nice 18-135. It's quite sharp but no IS and not so far from what you already have.

Now Sigma and Tamron both make fairly nice 18-200mm zooms at around half the price of the Nikon lens. They focus a little slower, don't have image stabalization, less optical quality, and don't have the build quality of the Nikkor, but if money is important and you use a tripod or good holding technique, the Sigma or Tamron offer the same zoom range at half the price.

I also have the Nikon 18-200. It is a great lens. I use it the most as it is
a very capable and versatile lens. The 3.5-5.6 aperture is very capable unless
you are shooting in low-light situations.

I have a D80 that came with 2 kit lenes, one is a nikkor 70-300 zoom with VR. Its a good lenes and can be bought cheap on ebay or craigslist for ~$300. This lenes will work great for objects up to 200 ft away if you want to snap wildlife or objects farther away than that, look at the Sigma 50-500, by all accounts this is a good lenes for the $.