I don't know if other conventions do this, or if this is unique to Atlanta's favorite geekfest.
DCTV (DragonCon TV) (http://web.dragoncontv.com/) is a collection of Adult Swim style bumpers, fake ads, and assorted other weirdness that plays on the video monitors in the various program rooms in between events. It's basically something to look at while you're waiting for everyone to get seated and the next panel to start. All of them are low budget, but that's part of the charm.
The site features some embedded in the blog entries, while other (mostly the older ones) require an extra click to download.
One of my favorites: Luggage Tetris (http://web.dragoncontv.com/videos/270/) :D
Also the iPatch (http://web.dragoncontv.com/videos/234/), Star Trek Lens Flare (http://web.dragoncontv.com/videos/338/), Thinkin' Strips (not embedded) (http://web.dragoncontv.com/videos/176/), and many more (http://web.dragoncontv.com/videos/72/) not included in these links.
Enjoy!
EDIT: or you could just go to their YouTube channel (d'oh). Here it is (http://www.youtube.com/user/DragonConTV#play/uploads/48/B9G04YawONk)
Another fav: Baby food ad (http://www.youtube.com/watch?v=wT3wTiQAYrY)