I just had to buy another computer and I found a great deal using Apple Insider's Price Guide for Apple devices. I have never, ever come across this page before and I'm genuinely surprised I don't hear about it more often. It is fantastic.
The page basically breaks down every Mac model (in every configuration too!) and lists the prices of the machines from several reputable retailers -- Adorama, B&H, MacMall, Amazon, Best Buy, Abt, and of course the Apple Store. Then, it just straight up tells you where the best deal is based on price. It's great if you already know exactly what machine configuration you want and just want to hunt down the best price online. I will forever bookmark this page.