Are exorcisms considered, in the various Christian Professions, an effective remedy for possession?

I thought they were just a curiosity from the past, but here's what I found on Wikipedia:

> Gabriele Amorth (born 1 May 1925) is an Italian Roman Catholic priest and an exorcist of the Diocese of Rome.

[Gabriele Amorth (Wikipedia)](http://en.wikipedia.org/wiki/Gabriele_Amorth)

Are exorcisms actually supported, encouraged, and, well, considered official catechism by the various Christian religions?