Er, quite easy to calculate actually.
The formula to find Hyperfocal Distance is:
Sq of Focal Length
------------------ (mm)
CoC x Aperture
where CoC (Circle of Confusion) for your D80 is 0.02, and Aperture is f/stop number.
In the field, if your hp is without a calculator function, use Denosha's method which is fairly workable.