If you have yet to be familiar with Ustream, it is a service that allows you to stream content live to their site and allow your viewers to interact via chat or polls, etc.  This functionality is now available for your iPhone.  You can live stream over 3G and Wifi and even setup polls and such for interaction.  After surprising everyone with its approval by Apple you can get this app now for free and try it for yourself.

[Ustream]