on the D80 go to option 22 built in flash, move down to commander mode and select OK
now on the flash hold sel for 2 seconds scroll right and press sel, move down to remote and press sel, now it should work remotely make sure the built in flash is open
Hope this helps.
Yep, done that....HAVE YOU POPPED UP THE ONBOARD FLASH?
you need to have the pop up flash as it triggers the SB800, you should be able to actually turn it off in the commander settings so whilst you will see it flash in order to trigger the SB800, it won't actually be flashing during the exposure if that makes sense!
The pop up flash is supposed to flash in commander mode, that's how it triggers the SB800, but if you set the Built-in flash mode to "--" in the menu it shouldn't affect the photo (and remember to reset to TTL if you want to use the pop up flash by itself, otherwise you see it go off, but wonder why your photos come out dark).