Via CNS, an interesting suggestion from Rome:

VATICAN CITY (CNS) -- Homilies should be no longer than eight minutes -- a listener's average attention span, said the head of the synod office.Priests and deacons should also avoid reading straight from a text and instead work from notes so that they can have eye contact with the people in the pews, said Archbishop Nikola Eterovic, secretary-general of the Synod of Bishops.In a new book titled, "The Word of God," the archbishop highlighted some tips that came out of the 2008 Synod of Bishops on the Bible. The Vatican newspaper, L'Osservatore Romano, reproduced a few passages from the book in its March 10 edition.The archbishop wrote that it's not unusual for preachers to recognize that they have less-than-perfect communications skills or that they struggle with preparing homilies. Everyone should spend an appropriate amount of time to craft a well-prepared and relevant sermon for Mass, he said.He said Pope Benedict XVI starts working on his Sunday homilies on the preceding Monday so that there is plenty of time to reflect on the Scripture readings from which the homily will draw.

Papal homilies always seem to go over that, if I recall -- not that there's anything wrong with that, actually. I grew up with 50-minute sermons from lay preachers, so a nice 20 minute homily is fine by me. Though I thought 12 minutes was the general guideline. Bloody Vatican, always changing things!