John Baez posted a link to a page
where he has movies (for viewing or downloading) of his low level discussion of E8 and Kostant's more particular discussion of E8 and Garrett Lisi's recent Theory of Everything paper. There are also some links that point to purely group-theory criticism of Lisi's efforts. If you have questions, I am not
the person to ask. I'm about a quarter of the way through the elementary one.
E8 is a Lie group that gives rise to some beautiful graphic representations (maybe this should be cross posted to math art) and also arises in string theory, so perhaps it is not surprising that Lisi was able to make interesting use of it.
crossposted to my journal and physics