How to have my shutter open for 30 seconds on my nikon d80 slr camera?

I want to take some night photos and get cool streaks, but i need my shutter open for more than 30 seconds more like 10minutes or 30 i have a nikon d80 slr camera.

You will have to set it to "Bulb" mode and then the shutter will remain open as long as the shutter button is pressed.
A better way would be to fix it on a tripod and then use a cable release for as long as you want the shutter to remain open.
I'm not sure if D80 has a wireless remote or not, but if it does, that would be the best. I'm sure if you Google you will find a lot of intervalometers and cable releases for your camera.

Do what Raj says. That is what I was going to post too. I use the D80, with a cable button release. You can slide the button forward to lock the shutter in an open position and just leave it there for as long as you need.