Unsweetened plain dairy free yogurts??

Nancy's makes a soy one. You could also look into making your own - http://www.culturesforhealth.com/learn/yogurt/how-to-make-non-dairy-yogurt/ or http://lifeoffthelabel.com/homemade-vegan-yogurt-no-equipment-required/ may be a place to start.

I bought some to get started, but now make my own from soy milk. It's pretty simple. Higher protein milks will be thicker than, say, coconut milk.
You just heat the milk to 115 F, stir in a couple spoonfuls of yogurt (store bought or homemade). I then put them in jars in the oven with the pilot light overnight (8-12 hrs). The longer you leave it, the thicker and tangier it becomes.

I like unsweetened sodelicious coconut milk plain yogurt and nancys. I hope silk comes out with a plain one soon.