Nothing compares to the real Chicago Style hot dog: Original Vienna beef hot dog, steamed poppy-seed bun, green relish, onions, sport peppers, 2 small cucumber slices, onions and mustard.
The fixins can be ordered online directly from The Vienna Beef Company at:
http://www.viennabeef.com/
In my travels I make it a point to find a Vienna Beef hot dog stand. My favorite is a place called Mustard's Last Stand in Denver, CO. Great stand neear the University. If you bring them a picture of another hot dog stand that serves Vienna Beef then you get a free hot dog. The pics are posted all over their walls.