For used binoculars, I'd say the Birdforum classifieds. Great folks, and they take care of the bins. Decent prices too!
For new, brick and mortar, local store: Wild Birds Unlimited in Novato, Ca. I stop by there every chance I get, even though its a bit of a drive. They carry some Zeiss, Swarovski, Opticron, Nikon, and Vanguard. Good selection, and you can compare different bins. I brought my first 'serious' birding bins from them. They match internet pricing, and are generous with their time.
Internet: I've had good service from Cameralandny, B&H photo, and Sport Optics. By good service, I mean prices and returns. Of the three, Cameraland was the most personable due to Doug being on the forum, and Neill on the phone.
