You can use the Nikon ML-L3 on the D50 with a bulb function, so I would expect the D80 to be the same, but no promises. I know that the D80 accepts more remotes than the D50 does, so it may not allow the bulb on the ML-L3.
The ML-L3 was the first thing I bought for my D50 after the Hoodman H-D50. I use it constantly in bulb mode and for other times when a remote is needed.