I love hummus as a dip for veggies. I buy Trader Joe's eggplant hummus, which is only 35 calories per 2 tbsp. Cooking Light also has a great recipe for Roasted Red Pepper and Cannellini Bean Dip
that is only 62 calories per 1/4 cup. It is super easy to make if you have a food processor. You might search on Cooking Light for other dip recipes; I've found them to be a great resource.
In terms of salad dressing, I'm afraid that I'm more of a vinaigrette fan, so I don't have any recommendations for low cal creamy or ranch dressings. I did try Wishbone's fat free Ranch and I was pretty disappointed, so I'd probably stay away from that. It was edible, but I was glad to finish off the bottle and move on to something else. I did try a brand called "Follow Your Heart Low Fat Ranch Dressing" that was better (although it still doesn't make my list of favorites).
My favorite salad dressings are:
Bernstein's Lite Fantastic (25 cal/2 tbsp)
Maple Grove Fat Free Greek Dressing (15 cal/2 tbsp)
Trader Joe's Fat Free Balsamic Vinaigrette (25/2 tbsp)
Trader Joe's Raspberry Vinaigrette (35 cal/2 tbsp)
Trader Joe's Sesame Soy Ginger Vinaigrette (35 cal/2 tbsp)
Carmela's Mediterranean Mystique Vinaigrette (40 cal/2 tbsp)
I also really like a good fig-infused balsamic vinegar as a salad dressing. I buy the Bistro Blends
brand, but someone else has recommended the Cyber Cucina
brand to me as well, which is a little cheaper if you are ordering it online.