Quoting Mama Rice:" I have not been able to find a low calorie salad dressing I like. I hate balsamic vinegar based dressing. ... [snip!] ... based dressing I have ever liked in blue cheese. What low calorie dressing (or dressing substitute) do you use on your salads?"
Have you ever tried just squeezing lemon juice on a salad? It's surprisingly good and it's not something I think I would usually like. Another thing to try is using a regular dressing but just not using very much dressing. Instead of pouring it on the salad, just pour like a one ounce portion in a little cup and dip each bite of salad in a bit of dressing. It really doesn't taste very different than drenching your salad in dressing.