It is based on the zipcodes from the US Census.
You put in the zipcode or range of zipcodes you want to add to your config file, and then write out a Modo compatible config.
Pretty easy to use, only Windows currently.
Be careful, you can easily make extremely large configs. There are over 42k in possible records, and if you put in the wrong range of zipcodes, look out! :) You can edit the results field before you write out the config however.
You can download it for free from here (http://www.radicalpixel.com/free_software/Modo%20Physical%20Sky%20Coordinate%20Generator.zip)
It is freeware, use it as you wish :)