Yes, Parkerizing. (Technically, Parkerizing is a phosphate process.) A few years ago I was working as a contract machinist for several gunsmiths in my area, and they were charging $50 for a phosphate finish plus the few bucks here and there to strip/disassemble the weapon.
Caswell has a blackening kit for $45. I've used it before and really liked the results.
http://www.caswellplating.com/metal-...xide-kits.html