A few weeks ago, I had to deal with something that had yet to confront me as a teacher - one of my students committed suicide. I was informed by the college administration, and the campus mental health director offered to come speak to my class. It is a lecture class, but I have my students do group work, so several of the students who had worked with this student were quite upset. It was a rough time, but I'm glad the counselor came and talked to the class. At least one student from that class has gone to seek mental health counseling since, so some good came from it.
I'd also like to say that I would never have suspected this student to have been in trouble from his demeanor in class. You know how after every Virginia Tech-type tragedy there is the outcry to somehow identify troubled students? If I had been asked to provide a watch list, he would never have been on it. He was outgoing, participated everyday, had made friends... the class was stunned to find out what had happened. His family and friends have my sympathies.
On a lighter note, I used Saturn's annoying tendency to gain more moons as a way to talk about how technology enables more discoveries, how the moon is small because otherwise we'd have seen it before, and how silly it is to memorize facts (how many moons Saturn has) as opposed to understanding processes (most moons are small, captured objects, etc...). Having such an example of a fact that changed since the last class seemed to have an impact.