While I'm not aware of anything specifically that protects your finish against road salt, I wouldn't underestimate the protection offered by a good quality wax. I've been using a product called Collinite 845 Insultator wax and it seems to hold up great against the weather. Granted, I live in Florida now (and have to worry about a different set of nature's elements) but I selected this wax because of its durability and longevity. But, really any quality wax should provide ample protection for you. One application before the snow starts flying might be enough to get you through winter, but if you can, reapplying sometime in mid-January would be even better.

Just be sure to apply it in either a heated garage or while the weather is still warm since if the temps drop too low, the wax won't bond to the paint's surface well.
One other thing that wasn't mentioned (depending on what kind of car you have and what type of tires you're running on) you might want to look into getting snow tires.
Unfortunately, this is my last Florida "winter" so I'll soon be in the same boat! Good luck!
TR