I love waldorf salad, but have lightened up my dressing quite a bit. I use equal parts mayo and plain yogurt(usually greek yogurt because that is what I always have around) - add a little sugar, either fresh lemon juice or apple cider vinegar - just to taste. This is good on fruit salad, like waldorf, but also makes an amazing dressing for a veg salad - I don't think the dressing suffers from using the lower fat versions of both the mayo and yogurt.