I think almost everything can be called an art ;) but it is a hard question. Art is a human actions that influences culture, comes from human creativity and puts aesthetics on the top of priorities, art is not necessarily useful. It has many different forms: visual arts (drawing, painting, sculpting), literature (poetry, epics, drama), performing arts (dance, music, film, opera). Both prehistoric cave painting and modern performances are art.
Things that cannot be called an art are those which main goal is to be useful and don't have to be even aesthetic.