Some of the earliest known forms of gargoyle have been found in ancient Roman and Greek ruins and were made of terracotta. Later figures were carved of wood, with a complete shift to stone by the 13th century.
Gargoyles were originally intended as waterspouts and drains to keep rain water from damaging the foundation of buildings. According to Wikipedia the term gargoyle comes from the Latin gurgulio, and the Old French gargouille, not only meaning throat but also describing the gurgling sound made by water as it ran through the gargoyle. Superstition held that gargoyles frightened away evil spirits whilst also serving the practical function of getting rid of the water. After the lead drainpipe was introduced in the sixteenth century, gargoyles were largely redundant and primarily served a decorative function.
Although most have grotesque features, the term gargoyle has come to include many types of stone statue. Some gargoyles were depicted as monks or combinations of real animals and people, many of which were humorous. Unusual animal mixtures, or chimerae, did not act as rainspouts and are more properly called grotesques. They serve more as ornamentation, but are now synonymous with gargoyles.
Gargoyles can be found in many types of Gothic architecture, but they are usually associated with the great churches and cathedrals of Europe. The picture to the right is of a gargoyle overlooking Paris from the Notre Dame's Galerie des Chimères.
I've found a really good site by a sculptor/stonecarver called Walter S Arnold.
This guy is based in Chicago in the United States and carves all manner of Gargoyles, from hamburger eaters to hamsters !
Take a look around his site and you will see that the art of the stonemason and gargoyle creator is alive and well (and living in Chicago!)