I'm impressed by djb's MCS 494 ("UNIX Security Holes") course. This was kind of famous at the time because students were taught to find real security holes in software as homework (and they sure did).

http://cr.yp.to/2004-494.html

http://it-beta.slashdot.org/story/04/12/15/2113202/djb-annou...

I have meant to work through this. It is very focused on C on Unix.