This application accesses the MABLE2k data base (rev. 7/10) with 2000 (and later) geographic codes, and generates "correlation list" reports / files.
Links: Geographic codes lookup (related app)   |   What's new in Version 1.3 | Previous Version (with 1990 vintage geos) | Tutorial (ppt)
There is now a tutorial comprised of videos of geocorr2k sample runs.
Note: The Help page has not been updated for the new 2k version. But an awful lot of what was true then still applies.