Grates, Hardware, Mirrors and More
This eBay store has a large selection of vintage, restored grates / registers.

Sarah and Keith
They don't have a store, but they have a lot of items listed. The majority of their items are door knobs, locksets, drawer pulls, and hinges. Definitely worth looking at.
(100% Positive Feedback)

O'Malley Tool Company
Amazingly good prices on power tools. They have routers, biscuit joiners, cordless drills, and more! They have really good feedback, too. Alternately, you can also buy from their website at: http://omalleytools.com/

Katesground
This eBay seller has vintage registers / grates.

Old House Nut Antique Hardware
This seller has a varying assortment of antique items.
(99.7% Positive Feedback)

J F Pegan Company
The J.F. Pegan Company sells light fixtures, repairs antique light fixtures/lamps, and custom builds Victorian-style lighting.
(99.9% Positive Feedback)

J White Antiques
This seller, based in Chillicothe, Missouri (a nice little town on US 36), offers a wide range of antique items. They also sell custom-made cabinets, kitchen islands, etc that they've made from reclaimed wood, such as beadboard wainscot.
(100% Positive Feedback)

House of Antiques hardware
A seller of very nice looking reproduction hardware including, window sash locks, door locksets, window lifts, electrical hardware, cabinet hardware, and more!

Olde Century Colors
Makers and sellers of historic paint colors in latex, oil, and simulated milk paint. Located in New Carlisle, Indiana.

Heritage Village Colors
Makers of historic paint colors in latex, oil, and simulated milk paint. Colors are created using natural materials and are based on colors from places such as Williamsburg. Located in Philadelphia, PA.

Reggio Registers
Makers and sellers of reproduction registers and grates for historic homes.