To clear up a few things. 1) The action photography I do is almost exclusively outdoors which, is was mentioned means I need a large aperture in order to achieve the shutter speeds I need. What would an acceptable aperture at the long end be for something along the lines of an 80-400 zoom telephoto? I ask because there is such a Nikkor listed with f/4.5-5.6?
The 80-400VR isn't a great lens, and f/5.6 requires 4x the light of f/2.8 for the same shutter speed. Unless you're shooting summer sports in a place that doesn't have many cloudy days, I'd avoid it, and if you are, I'd recommend the Sigma 50-500 instead as the extra bit of loss of light is made up for by the sharpness and extra reach IMO. I own the 80-400VR and have owned the Sigma 50-500.
2) The wide angle for architecture is clearly the way to go, thanks for the suggestions. Any thoughts though on zoom vs. prime (I know compuwar mentioned the 35mm f/1.8 which looks very tempting)?
Everywhere I can, I shoot with either my 35-70 or 20-35 at 35mm and stitch, but that's mostly exteriors. For interiors speed is necessary, so the 35mm looks to be a bargain- I have a Sigma 10-20mm, but find myself using it less often these days than when I first got it, mostly for those times when I can't back up far enough to use something at 35mm or 60mm. The Nikon 12-24 is also a good choice, but more expensive than the Sigma. You can rent the Sigma and Nikon and choose.
Really serious architecture shooters are going to spend really serious money on perspective control lenses or a bellows. A lot depends on what you consider architectural shooting and if you can stand to use a tripod- if you can use a tripod, then even the kit lenses won't be too bad at the wide end and stopped down.
3)compuwar, the telephoto is obviously where I am going to be spending the most so I want to skimp as little as possible within reason. Is the aforementioned 300 f/4 "good" or merely "adequate" relative to the f/2.8? What are the negatives of shooting at a higher ISO in that kind of situation?
Absolutely nothing touches the 300mm f/2.8 in terms of absolute sharpness, however the 300/4 is good to very good (I own one, but if I didn't have a 400/2.8, I'd definitely own the 300/2.8 instead of the 300/4.) You'll have to shoot a stop faster (remember, each stop is half or twice the light depending on which way your traveling,) which will mean more noise, and potentially not being able to shoot indoors in dark gyms/arenas/rinks or evenings. The positive side is that the 300/4 doesn't require a monopod. The 200-400VR is an obvious choice for wildlife and sports if you can shoot at f/4, but it's out of your price range. Sigma also makes a non-stabilized 300/2.8 that's still a raftload of money, just a smaller raft than the Nikon.
4) Someone mentioned Bjorn Rorslett's. I have looked (or tried to look) at his reviews and found it very difficult, not because the site is bad at all, but because there are so many similar lenses and the abbreviations that differentiate them are probably meant for someone with a little better knowledge of Nikon's labeling system. Are there any good sights that will give me a crash course in Nikkor lenses?
Many of the lenses Bjorn rates are much older lenses that are AF-D, AIS or manual focus only. AF-D lenses will AF on the D80, but will likely be slower on any of the consumer/prosumer bodies because the lower voltage batteries don't seem to do as well turning the screw. AIS lenses are oldies but goodies. These days though, many used Nikkors are expensive enough that you're better off getting a newer lens IMO.
Paul