The folks who first showed us video streaming live from an iPhone, Qik, now have an official (non-jailbreak) app available in the App Store.
Like Ustream Live Broadcaster, Qik Live [iTunes Link] is a free iPhone app that streams live video to a web page where friends, relatives, and the world at large can watch and hear what you're currently doing. Qik Live has a very streamlined interface that's simple to use. You'll need to sign up for a free Qik account before you start blasting your video to the world, but you can do that from within the app. The app runs on iPhone 2G, 3G, and 3GS devices on 3G or Wi-Fi networks.
Once you've launched the app and logged in, a pre-broadcast screen appears showing a live image. Settings are changed by tapping on a 320 x 240 landscape image to bring up a small menu. The menu options include muting/unmuting sound, turning chat on/off, setting a video to private, editing the title and description of a broadcast, choosing where to share the video, or sending the last stream to someone via email.