Holland Farms makes a 7oz Gouda cheese wheel that comes in a wax coating. It's perfect for a 3-5 day trip, and because of the wax, only the last surface you cut is exposed. I try lots of different cheeses at home and Gouda is one of the few cheeses I have problem with mold. Pepper Jack is another good cheese -- I think the peppers make the cheese acidic and prevent mold from forming as fast. I don't know how true that is, but Pepper Jack also seems to last longer than the other cheese I try.

If you have a Whole Foods near you, they have a tremendous selection of cheeses.

You can also seek out a local cheesemaker for a firm cheese. We get Raclette from Black Star Farms (along with a liter of wine) when we visit the Sleeping Bear Dunes. I like a salty cheese like Raclette or Parm when I've been backpacking or paddling all day.