The only thing I knew for sure that Agave was used for was in the making of tequila - saw that on a Globe Trekker episode once. Agave is also commonly knows as Century Plant and American Aloe. Most agaves are greenhouse or houseplants here, though there are a couple that can be grown outside if kept dry in the winter.
The agave is at the center of the economy of some Mexican country-dwellers. It furnished shelter, food, drink and soap as well as materials for fiber. Medicinally the juice of the agaves has been used as a diuretic and especially as an antisyphilitic. It was estimated that there were 371 different uses to which it is put in Mexico.
In Mexico the upturned leaves serve as shingles, the juice in ecvery state is usable and the plant is grown as a money crop in vast plantations.
These are large plants and I regularly take off the 'pups' that are a more friendly size and give away the large parent plants to people with more inside space. Most also have thorns along th edges of the leaves. Mine live in the greenhouse in the winter and out in the garden in the summer. They are carefree plants and their only drawback is that as mature, old plants, once they flower they die, but since they can live for a hundred years - hence the name Century Plant - it's not something most of us are going to have to worry about.