Protein Powder

I used Optimum Nutrition 100% Pure Whey Gold Standard (the one you referenced below) for years until I found Dymatize Elite Isolate. I believe they have a "natural" line too. I like it much, much more than the ON (and I've used shakes for 9 years).

I'm not expert but in a nutshell...there are several sources of protein that can be used in making the protein powders and there are TON of protein powders and ready to drink protein drinks out there. What you buy should depend on your goal. The one most people tend to use is whey protein (derived from milk/ dairy). If you want the most pure form look for anything that is 100% whey protein ISOLATE, that is the purest form of whey and has little to no lactose/ sugars and or fats and usually costs more, but it the best absorbability (I believe its about 100% or somewhere near that). Other options are whey protein concentrate, they are less concentrated versions and therefore lower absorbabilty levels of the protein and have some sugars and fats. There are also protein powders made from soy and other alternative proteins for those that are vegan or don't like whey, but overall whey is the preferred protein supplement for body building and weight loss because of the high absorption level (i.e. your body uses nearly all of the protein) which helps promote muscles.

This is a website I used for myself when I first started with the proteins it talks about the different sources and has more sciency info http://www.bodybuilding.com/fun/vinced7.htm

P.S. The optimum that many talk about is form GNC but every health/ nutrition store has their own brand.

Personally I use NutraBio 100% Whey (only available at their website) and also Nectar Proteins (both the 'sweets' which are the creamier ones and the 'juice' once which mix great with water!) which you can buy online or at the Vitamin Shoppe or some similar place and for ready to drink I use Premier Protein from Costco which is whey protein concentrate and only for those times I forget my protein powder or I'm on the go and dont have time or dont want to mix up a drink. I have also tried the Muscle Milk and Pure Protein RTD but I'm not a big fan of those. There is also Isopure 160 calories and 40grams of protein, no fat, sugar or carb and comes in 'juice-like' flavors, which I ok but has a weird after taste, many I spoke to consider this to be one of the best but at $4.00 a bottle I rarely drink it.

Kindda overwhelming I know lol. Good Luck and dont be afraid to try different brands till you find one that you like.