Some other recent posts illustrate that all over the country, we are trying to match and replace old wood trim, and that the sources aren't so easy to find, but they're out there. So I wonder if it would be useful to have a thread in which sources are listed?

So my big find is Tanex Industries Moulding and Millwork in New Westminster, BC, Canada.

Some specifics that may be the same or different at other shops:
Their mouldings are scaled down just slightly from the originals due to modern lumber dimensions, but the profiles are accurate. And like most millwork shops, they do custom work as well. They work in both fir and MDF. And finally, not everything is in stock all the time; as others have mentioned here, there is a minimum order size or set-up charge if you need something that is not in stock.

KarinL

A good lumber yard can run just about any molding you want, the problem is usually the knife setup charge.

You can also create them on a router table yourself, though it may take multiple passes and some other tricks (like a tilting setup for the router).

While I attempt to preserve and re-use old moldings, the labor in this needs to be weighed against the cost of making and using matching new material.