What factors are most important to you? Amount of protein per serving? Types of protein (ie. whether you want a blend or not), taste?
For
price, you can't beat
100% Whey by ON (24g per scoop), or sadly GNC 100% Whey(20g per scoop) at least when it's on sale. But as stated before, save yourself trouble and avoid GNC.
For
taste, refer to this thread:
Best/Worst tasting protein powders
For
blends, I like ON's
Pro Complex (55g's for 2 scoops) if you can afford it, not just because of the formula but it tastes good and mixes well...just can be a little pricey. Another good blend is Probolic-SR by MHP (20g's per scoop), which has whey along with other, more slow digesting proteins.
Finally, if you just want like pure, whey protein isolate try Isopure (50g's for 2 scoops...I think) because it's ideal for a post workout shake due to the fact it's isolate and will absorb faster and more fully.
On the subject of
Creatine, I'm a big fan of TRAC by MHP (about 28 servings per container, 4g's of Creatine per serving). There's no sugar in it and has given me very good results.