If you're planning to teach to beginners, I also would recommend TextWrangler from Bare Bones software. It doesn't have a lot of bells and whistles but is free, easy to use, and was written specifically for Macs. Won't confuse new coders and can be considered a gateway editor to introduce them to code editors in general.
-- Mark Vega Programmer/Analyst University of California, Irvine Libraries - Web Services --
