I use whey protein powder for making low carb cakes and biscuits!
I also use them when I come home from work and am hungry but want to work out. They quickly suppress my hunger and my belly is not bagged up enough to stop me working out. They can be used before or after workouts to build muscle. I also use them for packed lunches. My favourite one is Holland and Barrett's "Very Berry" for drinking. For baking I use vanilla flavour. I have no idea why this happens but the chocolate flavour makes me constipated. (I know! Too much information!).
If you do buy wait for Holland and Barrett's half price promotions as the tubs are very expensive.