Just when I figured the modern programming world was all about high-level-languages, I've started seeing signs of assembly language here and there. Recently I got to spend some quality time with Wolf Rentzch's amazing mach_override and mach_inject, which reactivated an old urge to learn more about PowerPC assember. (I can code my way out of a 680x0 assembler, but PPC? Not so much.)
There are a couple of new books about this venerable art, and there's been a bit of buzz in the Mac developer corner of the blogosphere about assembler. MarkD posts a list of links about the subject, and Wolf ruminates on the topic.