I talked about using magic in your presentations a while back in v2n9 http://www.antion.com/ezinebackissues2000.htm In that article I briefly mentioned that the "patter" or what the magician says is frequently the way the fun is added to the magic trick.
Let's look at patter for speakers a little more closely. Patter when you aren't using magic could be things you say while someone is participating in a demonstration on stage or it could be while they are coming up to the stage or when an unexpected occurrence happens while you are speaking.
Suppose you were doing some kind of demonstration that required the participants to put paper bags over their heads. You could be cracking one liners like "Don't worry. This bag has been sanitized for your protection." Or, "This bag has been known to improve some people's love lives"
If a participant is walking toward the stage slowly, you could hum the Jeopardy theme or say something like "I think I'll stop by Starbucks and have a triple Frappechino Latte with foam, whip cream and cinnamon while I'm waiting for you to get up here." Of course you would say this in a fun rather than attacking fashion.
When something happens that totally distracts the audience like a police car siren going by the building, polished presenters use a form of patter called "Pre Planned Ad libs" like "Oh, My ride is here" or "I knew I shouldn't have taken my wife's anniversary present as a tax deduction."
Pay attention to the situations you either create on stage or in the audience and to the potential distractions that may occur while you are speaking and create funny patter lines to use during those settings and you'll really add polish to the entertaining parts of your talks.