Gun Parts Corp - Biggest source of gun parts in the world

Brownells - Major gunsmith supplier, carries Renaissance Wax, which I recommend for preservation of antique & collector firearms.

Exploded Firearms Diagrams - no, not the "hot-handloaders homepage" - assembly/disassembly drawings.

Info Exchange - has some diagrams & manuals for firearms, downloadable for fee. 

Doug Turnbull Restoration – I always urge restraint in restoration efforts. If you are set on tackling it, Doug is one of the best, plus a great guy.

David Chicoine - The expert in antique S&W repair & restoration

Jim Horvath has quite a few antique S&W parts, no website, but email DriftDive56@aol.com

Gunsmithing Only - Mike Allee, a great all-around local KC area gunsmith

Dangerous Dave, the Old Western Scrounger – Great source for obsolete ammo.

Sarco – lots of military parts, plus repro material

Ponderosa - obsolete gun parts

Trapdoor parts – Parts for Springfield Trapdoors.

GunGrip.com – NC Ord, source of good reproduction "hard rubber" type grips for older handguns, plus more.

Snake Oil - Another product I like for firearms lubrication & preservation.