I have a vivitar thyristor 2600-d lens is it compatiable with Nikon's or any other digital cameras?

Thyristor is usually associated with flash units.

You will have to look at the camera mount part of the lens and see if there is a N or C on it.

And no, expect for using that old a lens in manual only, it will not auto-focus or auto expose with the new DSLR cameras

My search turned up a Vivitar 2600 flash unit. Are you sure you know what you have?