Pinnacle has their Rippers setting for Savage Worlds; IIRC, it's steampunk horror. Deadlands also has some steampunk flavor, with the weird science stuff.
Castle Falkenstein is a fairly early steampunk RPG, AFAIK - released in 1994. It's available in PDF and POD via DriveThruRPG. Also, there was a GURPS Falkenstein.
Steve Jackson Games also has GURPS Steampunk books/pdfs for both 3e and 4e.
Space: 1889 might be the OG "steampunk" RPG, maybe? It was published in 1989. There have been many versions, using at least five different systems: the original system from 1989 (unique, AFAIK), a Ubiquity engine version, a Savage Worlds version (subtitled Red Sands), a D&D 5e version, and a system called Empyrean.