Well, that all depends on what the place you are having them done at needs. I work for an advertising company, and since we use Photoshop, we can use any file type out there, but most clients send us jpeg's. We saved them as CYMK .eps or .psd formats, but that was only after color correcting them for the printing presses we use. Buisness cards are a different area that we don't do, but I imagine that the company that you are going with will accept most file types, and just as a recomendation, ask for a hard copy color proof before you have them print it, just so you can give the ok.
I know that I am one with beauty, And that my comrades are one. Let our souls be mountains, Let our spirtis be stars, Let our hearts be worlds.