[Patchman]

As for the camera system, it's the lenses that makes the system.

Here's my rule of thumb:

Don't bother getting a "kit" lens.
I don't look at any variable lens (ie: 18x55) that don't have a constant F2 to F1.4 F-stop.
Sigma lenses are very good optically, at a very competitive price, but they're bigger and heavier than NIkkor lenses.

The most expensive Nikkor AF 35mm lens is only $400 (I think).

As for bodies, the D80 was probably Nikon's most popular model. It was around for quite a few years. Forget the D90. This was an evolution that lasted only 1 or 2 years, as a way to bridge the D80. The D90 was quickly replaced by the D7000.

As for weatherproofing bodies, it all depends on what you use the camera for. Since 2007, I've used the D80/55x300 Nikon lens almost exclusively for outdoor/wildlife photos. This is mostly in the winter, even when it's raining or snowing. But I do cover my camera, and not expose it directly to rain/snow. I could use my D200 body to do this, but it's way too heavy.

And regardless of camera body, when you come back into the house/car, don't go from 22-degree outside to a blasting 80-degrees inside. Leave it somewhere to give it a chance to adjust gradually.