Hispanic? Latino? A Choice of Words…

Is there a semantic difference between the terms hispanic and Latino? Do the words mean different things?
News coverage of Sonia Sotomayor's nomination to the U.S. Supreme Court has raised some questions about the usage of words. Sotomayor refers to herself as Latina. Many people have strong preferences one way or the other.
I looked at a few web definitions for the two terms. One difference is that Hispanic seems to cover people who speak Spanish, and usually restricts that term to residents of the Americas. On the other hand, Brazilians are usually included under the designation Latino.
Education Week took a look at the question recently.
June 17th, 2009 at 10:03 pm
Hispanics are Spaniards (Europeans)… everyone else is Latino; in the Americas, Latin based language, and from all sorts of backgrounds.
June 18th, 2009 at 7:54 am
I didn’t know that Brazilians are included under the designation “Latino”. That’s great because I love them!