A unique aspect of Ustream.tv allows you to stream live which could allow someone to log on during a certain during a steaming video and post questions or comments while the video is being recorded. This could allow a class to "tune" in to a streaming video and ask questions of the presenter and get answers in almost real time. Teachers are doing this in classrooms already there was an instance of a teacher using this to reinforce the knowledge of class on the differences in the grown cycle of different insects.
Students who are sick can watch classes online and ask their teachers questions on the material being presented and have them not to fall behind.
Another way to use ustream.tv is to also "borrow" teaching strategies from other teachers that have a live stream of their own class room this could also allow you to think of other ways to explain certain subjects perhaps in a different way in order to help a struggling student understand. This aspect can also allow you to be inspired on how to incorporate new activities in to your classroom.
On the business end, this application could allow a person to present to different rooms or other companies at the same time and ask questions live. This allows you to save on travelling and lodging to go to give a presentation or to watch a presentation. This works better than others because you not only can ask question but you also have a visual of the person and their visual aids, in comparison to other programs which if you are conferencing with more than one other group all you would have is audio which cuts out a large amount of the effect of your presentation. More importantly it's free.
Other ways of using this could also be doing sales pitches this could allow for multiple audiences and have them give you feed back and questions in real time allowing for a fast pick up of a product. It not only allows you to display and explain a project it allows you to have the presentation effects of real time video steam and Q and A abilities allowing you to reach a broad audience and allow them to know that you are actually there to answer questions and aren't just a recording and after the stream is over they can revisit and see the information over and over again.