I like Craig (Meathead) Goldwyn's Lexington Dipping Sauce. You can find his recipe and a thousand other tips and techniques on his wonderful website, Amazingribs.com.
This always gets rave reviews, and is terrific on ribs and pulled pork:
Yield: Makes about 1 1/2 cups.
Preparation time: About 30 minutes.
1 cup distilled vinegar (do not use cider vinegar)
1/4 cup ketchup
1/4 cup apple juice
1 teaspoon hot sauce
3 tablespoons light brown sugar
1/2 tablespoon salt
1 teaspoon crushed red pepper
1 teaspoon finely ground black pepper
Born just fine the first time, thanks...