If you live in an older building and favor historical and/or aesthetic continuity, Portland and Seattle-based Rejuvenation Hardware is a terrific resource. Specializing in period-authentic lighting, hardware, and house parts for old homes, it's also a great place to delve for fittings and fixtures if you're looking to introduce some Deco character or Arts and Crafts ambiance into a contemporary space that feels too stark.
Rejuvenation Hardware's stores and its web site carry a dizzying array of period fixtures and hardware, covering many popular American interior styles of the last 115 years. Browsing through this site's eight broad collections of light fixtures, lighting accessories (like switch plates, Victorian filament bulbs and glass shades), and various hardware doodads like brass doorknobs can take awhile.
This is a company that takes great pride in the quality of their products, and everything is well-documented and organized on their website. If you know what you're looking for or have even a few parameters (like a size limit) you can find what you need pretty quickly by browsing the collections via Styles, Types, Decades, Base Price, or Size.
If you don't know what you're looking for, browsing the site for inspiration via room type or customer pics can be a lot of fun. (The site also includes a "Chance" option and a Wizard that will lead you to products based on your answers to a series of questions.)
I used a couple of their light fixtures for a 1920's bungalow I renovated. They also have a house parts product line that includes doorknobs, switchplates, towel rings, soap dishes, etc which I like as well.
We bought our drawer and cabinet pulls here (the Portland store).
Part of the store is new hardware and light fixtures and part of it is actual vintage fixtures. They had some beautiful glass doorknobs and pulls and old carved wood mantles!
This store is an experience... And when you are done, its nice to grab a bite at the daily cafe located in the store.