As previously mentioned on this site, there are many useful text files in /usr -> share -> misc, containing such useful information as zip codes, airport codes, area codes and more. Problem is, the versions shipped with OS X are very out-of-date. Here's a little shell script that will update them.
#!/bin/sh
# update_codes.sh
#
# very simple script to update airport, phone and zip codes kept
# in /usr/share/misc from source data at the openbsd site.
base_url='http://www.openbsd.org/cgi-bin/cvsweb/~checkout~/src/share/misc'
code_list='airport inter.phone na.phone zipcodes'
for code_type in $code_list; do
echo "downloading $code_type..."
src="$base_url/$code_type"
dest="/usr/share/misc/$code_type"
mv $dest ${dest}.bak
curl $src > $dest
done
As previously mentioned here, you may use the very cool Code Finder utility to view and search these files.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20030806155951171