The food industry has attempted to accommodate low-fat diets by creating low-fat and fat-free versions of all your favorite salad dressings. Picking up a bottle of one of these is one good way to cut down on the overall amount of fat in your diet. Low-fat ranch, for example, can have as much as half the fat of regular ranch dressing and one-third of the calories.
Since these dressings vary widely in quality and flavor; you'll probably have to try several different types to find one that you like, but there are some reasonably good substitutes out there. Keep an eye on the label, though -- when the fat is removed, it's often replaced with other ingredients you don't want. In bottled low-fat and fat-free dressings, that often means high-fructose corn syrup or sugar.
Also, keep in mind that some of the vitamins and minerals found in healthy salads are fat-soluble, so going fat-free may not always be the best idea.
If bottled low-fat or fat-free dressings aren't for you, consider cutting the fat in other ways. If you're making vinaigrette, experiment with the traditional ratio of oil to vinegar (3 to 1), by cutting back on the oil and using different types of vinegars, juices, broths and herbs. Or, maybe you just need a squirt of lemon or a spray of walnut oil if your salad is already full of lots of flavorful ingredients. If you're making creamy dressings at home, try substituting low-fat or fat-free sour cream or mayonnaise for the full-fat versions. You can also use yogurt in place of sour cream in many recipes without sacrificing flavor.