Two that work really well for me are rhubarb and jicama. If you haven't tried them yet, give them a whirl.
With rhubarb, I cook it with spices and stevia. It tastes like applesauce.
Jicama I eat raw sliced up with either chili pepper and salt or cinnamon and stevia.
Here are recipes for both:
Rhubarb
Jicama