Protein is getting a lot of attention these days and rightfully so; it's not only essential for building muscle, but upping the amount of protein in your diet will keep blood sugar/insulin levels stable through the day, making you less likely to have an unhealthy snack attack from sudden hunger.  Though there are plenty of foods out there chock full of protein (chicken, eggs, soy) my choice of protein (besides a juicy steak dinner) is whey protein. 
Whey, a by-product of cheese manufactured from cow's milk, is a super source of protein for athletes, bodybuilders, those just looking to lose weight.  It has a complete amino acid profile and is absorbed faster than any other protein source, making it ideal for drinking after workouts and first thing in the morning when the body needs nutrients and amino acids. Also, whey protein isolate is the purest form of protein and contains the highest biological value of any protein source. Biological value (BV) is a measure of how quickly and efficiently the body uses a protein source and the higher the better. Just as a reference, eggs have a BV of around 100, whey protein isolate can go up to 150. Whey can help you lose weight since protein takes more energy for the body to process than carbohydrates and fat so more calories are burned, leading to a faster metabolism and faster weight loss. 
I drink my whey protein shakes at breakfast, before my morning workout and then again in a mini shake after my workout.  I have chocolate and vanilla powders to keep things from getting boring and I always add ice for best flavor and palatability.  Just 2 scoops of whey and I'm already getting 60 grams of protein — about halfway to where I need to be protein-wise…
Even so, I always keep a few scoops with me along with my shaker so if I get hungry on the road, I can just add water and shake for a perfect meal.  For those looking for other protein sources, say for those with food sensitivities and such, there's egg white, soy, rice and even hemp protein out there too.