I haven't had a bottled dressing in years, so no help there, but one thing I love is a good aged balsamic vinegar (10 or 12 year)--they're expensive but worth it. It's thick and sweet and a drizzle is all you need so it goes a long way. It's about 40 calories a tablespoon, but I almost never use that much.

The other thing I make (and never measure anything, and what all goes in it changes depending on whether I remembered to make it before we're sitting down to eat, lol) is soy sauce, rice wine vinegar, fresh or powdered garlic, maybe ginger, and a few drops of sesame oil. There are almost no calories, but it's loaded with flavor because the sesame oil is so powerful. You could sweeten it if you like a sweet dressing, with splenda or brown sugar.

Making a miso dressing is easy too--it gives a creamy consistency without sour cream or mayo (I think fat free stuff is bad for you so I never eat it). I mix in rice wine vinegar and a dash of milk, and garlic or whatever else sounds good.