I have a Tamron 17-50 f/2.8 that stays on my d300 90% of the time. I cannot recommend a lens in the 17-50mm range enough. I had the Nikon 17-55 f/2.8, but at 3x the price and 3x the weight of the Tamron, I sent it back. It's not any better, just looks more pro. I've owned this lens for over a year now. It was on my d200 all the time too. I beat the crap out of this lens and it just keeps coming back for more. Tamron customer service is top notch, as they warrantied a loose front element (did not affect image quality or function, just a rattle) very quickly. In a holster bag such as the
f.64 HCX large holster case, I can put my d300 w/ Tamron 17-50 in with lens hood on and no lens cap, and it's really quick and easy access, ready to shoot in seconds.
I just bought the Nikon 70-200 f/2.8 and it's really nice, but too heavy for anything but formal shoots. Excellent zoom range, as well as watertight which is nice here in the northwest. Quality of construction is ridiculously nice, with super-smooth zoom and lightning fast focusing. For truly professional results, you'll need this lens. I am looking forward to trying the new Tamron version as it will be much lighter. VR is a nice feature, and it really works amazingly well, but I have found that it limits me to a certain style of shooting, whereas without it you are forced to be more creative with light (which is a good thing at times). It also drains your camera battery significantly.
Sigma 10-20mm is sharp and has nice contrast, but the distortion is really bad for human photos. Landscape and nature works well. I may be interested in selling this one b/c I never use it.
Nikon 10.5 fisheye is AWESOME for close up shots. Clarity and contrast are top notch. This is the sharpest lens I own, and is quickly becoming my favorite lens. Super lightweight and tiny, allows really unique perspective. Only downside is you have to be REALLY close and only experience will allow you to know where the distortion will appear.
I had a Sigma 105 f/2.8 macro, but did not find it very useful due to slow focus and I don't shoot alot of macro anyways. Nice and sharp though.
When I had a d70s, I used the Nikon 18-200vr lens alot. Although it's quite dark most of where I shoot and I opted for f/2.8 instead, I constantly think of the 18-200. Great all around lens. Now that I carry remote flashes most of the time, I am thinking of getting another one of these.
I have been adding photos to a photo-a-day collection that you can view
here. You can read the metadata from the images to see which lenses were used. All of these photos are with D300.
You could not have chosen a better camera. I am constantly amazed by the capabilities of the D300. Good luck with lens choices, it's a never ending struggle.