Usually, schools try to get a mix. Someone famous and entertaining, and someone with all the real degrees (not honorary ones) to say wise things.
Here's a selection from this year from the celebrity speakers
JULIANNA MARGULIES speaking at Sarah Lawrence College's commencement ceremony
'I was so nervous [to speak], in fact, that I've done a bit of reconnaissance. I've read every graduation speech ever written. I sought advice from the smartest people I know, but mostly, I have been listening. Listening to your reflections on the school, listening to your plans postcollege, and listening to your thoughts on our future. Part of this listening was to help me write this speech, but selfishly, part of it was for my 2-year-old son [pause] because he has such a big stake in your actions. [She stops to wipe her eyes.]
Shortly after graduation, I got very, very, very, very lucky. I landed a role on a show called ER. It was a huge hit all over the world. I soon had money, accolades, status, and George Clooney. [Crowd cheers.]
NINA GARCIA speaking at Fashion Institute of Technology's commencement ceremony
"The fashion industry has a particular flair for making any slight feel as though it's the worst thing that's ever happened and any small victory as if it's the most extravagant accomplishment since the wheel. This emotional metronome can lead to a very surreal work environment — I promise that."
LISA KUDROW at Vassar College's commencement ceremony
''It's not like there's some kind of social network wherein I could communicate with such a large number of people at once...
...over the next eight years, my resolve and commitment was steadily challenged. Challenged by casting directors telling me to my face that I was horrible. Agents letting me know, 'It's hard; we don't know what to do with you. They want gorgeous on TV, you know? There's really not a place for you."
Listen to Kudrow here.
ANDERSON COOPER speaking at Tulane University's commencement ceremony
Trustees, honored guests, faculty, friends, and Who Dats — I was curious to see how the sign language interpreter would do 'Who Dats' — [Crowd laughs] thank you very much for inviting me here to speak on this incredibly special day.
...I don't need to give you advice today. I don't need to teach you, in this room, a lesson. The truth is, your class has taught me a lesson — and taught all of us a lesson. As you've heard several times already today and as you know too well, you are the class that came after Katrina. And even though you've heard it a lot doesn't make it any less true. You saw this city on its knees in those weeks and months after the storm, and yet you still applied to Tulane. You could have gone elsewhere, as the president said. A lot of folks probably said you were nuts to commit to New Orleans — some of your parents probably said the same thing. But you came anyway. You took a chance. You made a tough choice, but look at you now, look at what you've accomplished, not just for yourselves, but for New Orleans. Your choice helped this city rebuild, renew, and restart.
Cooper speech here.
MERYL STREEP speaking at Barnard College's commencement ceremony
"Being a celebrity has taught me to hide, but being an actor has opened my soul."
Alec Baldwin, the award-winning actor and alumnus of NYUs Tisch School of the Arts, addressed the graduates at that school's ceremony. He received a Doctor of Fine Arts degree, honoris causa. He gets lots of cheers, some laughs and tries to give some serious talk too on commitment.
View video of all the speakers at http://www.ew.com
In case you are asked to speak in 2011, here are some books to plagiarize: