I'd go with Vitamin Shoppe (
www.vitaminshoppe.com).
The prices are good and Vitamin Shoppe carries its own line of supplements, many of which are just as good as their commercial counterparts, but are cheaper.
Again, for those howling about the high costs of whey protein powder, Vitamin Shoppe's BodyTech line sells 5-lb. jugs of Whey Tech protein powder for $25.
The shipping is cheap, too; $5 for standard shipping (4-6 business days); $3 for "Super Saver Shipping" (3-10 business days); free shipping for orders $99 or more. And Vitamin Shoppe often has promotions (i.e. $20 off all orders $100 or more).
If I hace one criticism about VitaminShoppe.com is that it doesn't always carries some of the newer supplements. For instance, the online store has yet to start carrying IDS WaxiMaize or MuscleTech's Nano Vapor or NanoX9.
But, overall, the service is great. For those in the Armed Forces, Vitaminshoppe.com does deliver to FPO and APO boxes, for the same $3 Super Saver Shipping cost.