Unless you're willing to spend the big bucks on a 24-70mm f2.8 nikkor, then the best "normal" zooms are not nikon.
Check out the tamron 17-50mm f2.8 and the tamron 28-75mm f2.8. They are better then any of nikons "budget" normal zooms.
There are basically five price/performance levels of lens:
from cheapest/worst to most expensive/best:
1) no-name brand, ultra cheap and ultra horrible (typically cheap chinese lenses available online)
2) budget/consumer lenses from respected third party brands (tamron, sigma, tokina), some of these are good especially their ultra-wides and macro offerings.
3) budget/consumer lenses from nikon/canon
4) pro lenses from tamron, sigma, tokina--typically identified by fixed f2.8 apertures.
5) pro lenses from nikon/canon
Most people can't afford 5, but 4 is often a better choice then 3.