I've just completed a short video tutorial that explains the basics of using video in Second Life. I explain the basic concepts behind SL video and show you how to create a very simple video screen that you can use to watch videos on your own parcel of land. I also show you how you can use public domain and Creative Commons licensed videos form the Internet Archive. (archive.org)
You can find the video on my Shiny Life website:
http://www.shiny-life.com/2007/12/31/how-to-use-video-in-second-life/