Hugo Mills gives a short talk on GnuPG, a Free Software PGP replacement. This talk also covers some basic cryptography principles, but doesn't involve any mathematics!
See http://www.hantslug.org.uk/cgi-bin/wiki.pl?TechTalks for more details. This talk was given at the Hampshire Linux User Group (HantsLUG) meeting on 2nd February 2008 at Southampton University.