I sometimes teach Math 459, an advanced undergraduate course on computability and unsolvability. My course announcement for Spring 1998 is here in several formats: PS, PDF, DVI, LaTeX, plain text.
Chapter 1 of my Math 558 lecture notes consists of a somewhat different exposition of computability theory.
Also of interest is the Penn State Logic Seminar.
firstname.lastname@example.org / 5 December 1998