Roy Osherove reported a trick to watch the sessions of the US TechEd 2005. Paul already mentioned this posting. But it’s way too complicated: browsing one site and then composing the URL for another site.
Why not go to this URL: http://microsoft.sitestream.com/TechEd2005/
Update: Unfortunately this doesn’t work any more. You need to use the trick that Roy mentioned (link above).