"Unofficial" Serenity Viral Videos Emerge
These scenes do not appear in the movie, contain no real spoilers, and have not been acknowledged by Universal, but as they star actress Summer Glau and writer/director Joss Whedon they make for a pretty official unofficial viral marketing series.
When asked about the videos during a webchat at Empire Online, Whedon said, "...I also deny knowledge of those things that I wrote and shot and am in."
Site with various links to all of them, in different formats, plus FAQ: www.session416.com.
More movie info at the official "Serenity" movie site.