C&C per req:
My first comment is in fact a question: Why have your ISO set so high? Granted, that 640 isn't out of the question for a D80, but if you can get shutter speeds of 1/600 or greater, it seems to me that it would have been prudent to reduce your ISO to at least 320.
1. Nice image, good work on the eyes. I like the lighting in this one, nice and even; appropriate for the pose.
2. Two things strike me about this one: (1) She's squinting - watch the sun's effect on your subjects, and (2) DoF; too much of it. This one should have been at a much larger apeture to reduce the DoF, or by backing up a bit and using a telephoto. Either would have solved it and reduced the distraction of the background.
3. Nice, but a little strong on the highlights in her hair, and much too soft.
4. Good lighting and better DoF, but the expression really doesn't work. She looks quite unhappy in this image. I think it might also have been better cropped slightly higher on the bottom.
5. Cute pose/expression, but again too much DoF and slightly over-exposed. Make sure you know what you're metering, especially when the model is wearing white/light coloured clothing.
6. I really like this one, but again a little over-exposed. It would have been nice to have her looking slightly toward the camera as well.
Overall, I'd say you did quite well. The poses and exposure are good, with just a few minor technical considerations.
Just my $00.02 worth - your milage may vary.
~John