Sometimes the most exciting part of restoring a piece that requires hardware, is finding the hardware! This adventure is made easier for me when I go to my local Boston shop located in Brookline Village.
Village Green Renewal is an conservation-minded handyman shop that carries a variety of vintage hardware, but also serves as Brookline's go-to store front for the restoration and repair of your home goods. The store easily fits into the style that the New York Times recently called, American Rustic. Their dedication to the general craftiness and aesthetic of late 19th century America gives the store its authentic charm.
The hardware is abundant, but limited. A particular style of hardware has a finite number of exact matches, so you may not find as many as you need to achieve a consistent set. But you're bound a set that you like, or may find the perfect mismatched variety of vintage hardware.
Where are the local shops in your area that provide a similar array of vintage hardware and/or restoration services? Do tell!

Shaw's Original Fir...
The Old House Parts Company in Kennebunk, Maine. http://www.oldhouseparts.com/doorknobs.htm
Village Green Renewal is awesome and the owner is a cool dude. I love this place. Great local find.
I love this place! They repair practically anything.