Can anyone remind me if there's a machine readable copy of the MARC 
geographic codes available at any persistent URL?

They're in HTML at http://www.loc.gov/marc/geoareas/gacs_code.html . I 
actually had a script that automatically downloaded from there and 
"scraped" the HTML -- but sometime since I wrote the script, the HTML 
structure on the page changed and it broke.

(I kind of thought that was unlikely since that HTML page itself was 
machine generated -- but I guess they changed the software that 
generated it. Certainly I knew that scraping HTML was a bad thing to 
rely on... which is why I hope LC provides this in some format less 
likely to change?)