Bob's Red Mill has an unflavored whey protein that I really like. It is more versatile than the flavored mixes... I've even experimented with adding it to my baking recipes, in addition to the endless flavors of protein shakes that are possible.
Try
WHEY PROTEIN CONCENTRATE for product information. Also, check out the 2 recipes on there: Protein Fruit Smoothie and Cinnamon Bran Muffins.
Look for it in any grocery store that sells Bob's Red Mill products. If they don't carry it, they may be able to special order it.
I've found I prefer whey over soy powders, it's easier on my digestion, and has a better amino acid/nutrient profile.