Besides ON, which Steve already mentioned, I like trueprotein. They are by far my favorite. (But allow a long-ass time for delivery, if you're not living in the US.) I get the complete milk dairy isolate, which is 80% casein and 20% whey, but a bit pricey. I find it mixes nice and thick, and that the banana flavor + say 2 cups of blueberries and some cocoa = a party in your mouth.
I wouldn't drink muscle milk or any sort of "mass gainer" personally, unless it's a cost effectiveness thing. Just use fruit. More vitamins and such. And generally speaking, whole foods > supplements, so try to eat nice and clean from lean proteins, good fats (everything but possibly trans, in balance), and fruits + vegetables. Starches (from whole grains and tubers and whatnot, preferably) after weight training only, ideally, imo.
And there's always milk. Lots and lots of milk.

Any
protein shake is improved by the addition of milk, generally speaking. Whey is significantly more disgusting in water. Milk + quality chocolate
protein = fat free chocolate milk, with more
protein than sugar. Fat free chocolate milk + (1 cup milk to 30g powder) chocolate
protein = chocolate milk with evensies
protein and carb.
Also, I would google Berardi's "Massive Eating" and "7 Habits" articles on nutrition. Gaining size is a simple matter of calories in > calories out. But, getting plenty of
protein, and eating nice and clean (and healthy) surely won't hurt, and may even help, a lot.