I recently came across this essential viewing, a 55min recruitment style presentation by Jeff Dean of Google, at the University of Washington.

http://www.uwtv.org/programs/displayevent.asp?rid=2459

Those of you into security and redundancy will be very interested in the GFS (Google File System) and the way they manage backups.

From an SEO perspective what was intreaguing is the whole discussion on 'shards' and query handling.  It gets more interesting around the 45 minute mark, with insites into Googles conceptual understanding - trying to determine the meaning of the query rather than just what the words are, and also clustering of words.