Williams Brewing and Yakima Valley Hops. If I need something other than ingredients I shop several others and may order some ingredients to get the total up to a level that qualifies for free shipping, discount, or some other promo.
The only ingredients I buy on-line are hops and cocoa nibs, both by the pound (or two, for the nibs).
I use Hops Direct, Yakima Valley Hops, Label Peelers, Farmhouse Brewing Supply, buying on total delivered cost and availability. Nibs I get from Amazon...
I get most of my stuff from Ritebrew. I haven't seen their prices beaten by anyone, their shipping rates are reasonable, and I'm within their 2-day shipping area.
Ritebrew for most stuff
Sometimes MoreBeer if wanting some specialty grain
Yakima Valley, Farmhouse for bulk hops once or twice a year
Amazon very rarely for hardware bits
Morebeer and Yakima valley hops. I live in an isolated area and both companies often ship within an hour or two of my order being placed. It’s easier to calculate when I will receive the order than with other companies.
I have AHB 5min from work on the way home so I'm spoiled. Super very nice people and their point system is very nice. They even give you points on things you buy with points. Rarely something is cheaper in Amazon or they don't have it so I go there. Their prices are as low as lowest out there for most and their service top notch.
I mostly use MoreBeer and Atlantic Brew Supply. I like Atlantic Brew because you can purchase grains to the ounce... I typically buy ingredients for individual recipes. They only offer $8 flat rate shipping so I usually wait to order ingredients for several batches to lessen the cost.
Amazon Prime for lots of equipment (like tubing, barbed fittings, regulators etc) also I often get yeast and hops off Amazon.
Everything else it's usually Northern Brewer...shipping is free over $30, they have good quality grain and they're not far from me so it gets here quickly