StackOverflow has a lot of interesting material on teaching programming (and computing in general). Among the links is the following video. Don't watch it if you're not interested.
Nat Torkington lives in New Zealand and has spent the last couple of years volunteering as a sysadmin, computer club organizer, and teacher at his local primary school. He shares his experiences of teaching programming to 8-12 year olds in his blog (and also on O'Reilly Radar) as well as in this inspirational talk from OSCON 2008. His conclusion, a call to arms for geeks everywhere to help.