At PAX this year Wil Wheaton did one of the keynote speeches. While I've never made it to an expo of any sort at all I was surprised to see an MP3 of his talk online. After listening to him I must say, wow, what a geek, what a great geek.
You can download his speech here: Right click > Save As... (http://s3.amazonaws.com/media.penny-arcade.com/PAX07_Keynote.mp3)
NOTE: There is ADULT LANGUAGE and potential ADULT THEMES. This is NOT SAFE FOR LISTENING AT WORK and if you SHOULD NOT be listening to this PLEASE DON'T! I am not responsible for any accusations, claims and/or promises within this recording. While I do endorse the theme of the message I cannot speak to the accuracy of claims within the recording. Listen at your own risk.