Vulcan was a fire god entitled to a special priest, the flamen Volcanalis. The god's origins are in doubt. Although many Roman gods were originally Etruscan, Vulcan was not: the Etruscans had another fire-god, Sethlans. Nor were Vulcan's origins Greek, although eventually Vulcan was equated with the Greek god Hephaestus.
Vulcan's temple had to be located outside of a city because of its potential for destruction. Ceremonies for Vulcan may have included driving animals into fire and there fishing games.
Source: H.H. Scullard Festivals and Ceremonies of the Roman Republic
In Mommsen's chapter on Roman Religion, he describes the cycles of holidays for types of gods. Here is the section on the Volcanalia:
Handicraft and art, on the other hand, are represented in this cycle of the gods only by the god of fire and of smith's work, Vulcanus, to whom besides the day named after him (Volcanalia, August 23) the second festival of the consecration of trumpets was dedicated (tubilustrium, May 23), and eventually also by the festival of Carmentis (Carmentalia January 11, 15), who probably was adored originally as the goddess of spells and of song and only inferentially as protectress of births.
Mommsen Book 1 Chapter 12
Tip on identifying pictures of Hephaestus/Vulcan: look for the raised, lame foot.