I have used a couple of different brands, but I like these two the best: EAS Precision Protein, and Designer Whey. Both, when shaken, lose their lumps nicely, but the latter stirs better if you don't have a shaker. They're both low carb, low sugar and low sodium, and they're both made from protein isolate, so they're absorbed into your system very rapidly. I never buy them in a store; I always do a froogle search and then do an online store price comparison to get the best current buy.
Since you mention that fitday says your protein is low, may I ask if you have considered increasing your intake of plain ole lean protein food? I do the protein supplement to make sure I'm getting my day's allotment of protein over 5-6 meals, but I still make a point of eating fish, chicken, turkey breast, cottage cheese, and the occasional lean beef. Hope this helps!