Nikon Sb-400 Flash Unit

Any third-party flashes off camera work?
I have a Nikon D60 and I'm wondering if the third party flash units that work with my camera. Or is it just a Nikon thing? I need one I can control separately on a tripod, etc. .. Any ideas? I need an equivalent to the SB-400 and SB-600. Something not too expensive choice.
I bought two very cheap flash units (some no brand) to use through its role in slavery optics to illuminate my backdrops, etc. So is the idea .... The cheapest way is to go through optical flash. You need a flash on the camera (although built-in flash to do) to activate the other (s).
