DPSNutrition.com is good
MassNutrition.com
Protein Factory.com - These guys have several types and formulations of protein, also you can customize your own formulation.
DPS is good. I just ordered 10lbs of Optimum Whey from eSupp Supplements for $46 (couple bucks cheaper than DPS). The only thing I don't like about DPS is you have to order over the phone if your billing and shipping addresses are different. I'm at college so I still have my bills sent to my home address, so this is kind of a pain in the ass. Probably not an issue for most people. eSupp uses Yahoo so you can use Yahoo Wallet to easily order stuff. When prices are so competitive, its the little things that make the difference.
i buy mine at gnc, 50 bucks for 87 servings, also buy one get one half off, also 20% at the first tuesday of the month, that is 60 bucks for around 174 servings of 22 grams whey protein, i think that is a good price. also if u dont want stores try www.supplementdirect.com they have good prices.
i use thoes guys sometimes their shipping is better than dps but prices a few bucks more. But still very good prices. THe shipping is a flate rate i think (up to a certain lb) and its 3 day select. I just bought 10 lbs of N-large & Creatine from fitsavers because in the long run w/ shipping and everything @ DPS its cheaper