When there's just a tiny bit of mustard left in the jar, don't throw it out. Instead, toss in a few ingredients, and shake a tangy Dijon vinaigrette right in the container. A crushed garlic clove, some chopped fresh herbs -- tarragon, for instance -- and minced shallot will add the right flavor. Pour in balsamic vinegar, season with salt and pepper, then close the lid and shake. Add olive oil (3 parts oil to 1 part vinegar); shake again to emulsify the dressing, and then drizzle over your favorite salad. With a tightly sealed lid, the dressing will keep in the refrigerator for up to one week.