I have always wanted to be good at public speaking, especially in front of large audiences. Although, I can address a gathering without a shiver in my voice, I nonetheless feel butterflies in my stomach all the time!
I found some interesting links that might help soothe those tense moments!
Most times, one hardly derives anything at the end of an hour long technical presentation, and more often than not, the content of your presentation is lost after your audience exits the room.
The author in the above link suggest that how adding some humor, may help in retentivity of the subject in the minds of your audience.
Very nice link that tells how humor is hidden in content more than in a few one-liners that you add to your speech.
Another nice essay on FUN-talking