Does a flash for a 35mm Nikon SLR work with a Nikon DSLR?

I need a flash for my D3000 and my dad has a couple flashes for his 35mm Nikon. Would those work on my camera or do they only work with 35mm SLRs?

I don't think I'd risk it. You can damage the camera that way.

You would need to provide more information on the flashes or look up the flash information on a list like http://www.botzilla.com/photo/strobeVolts.html

Some older flashes can have a feedback voltage of 250+ volts which can fry a DSLR if it can't handle it.

It should work. In my experience the only problem you get is down the iTTL playing up. In purely manual mode it should work fine.