http://www.nationstates.net/pages/api.html
This has previously been known as regiondata.cgi and nationdata.cgi,
The API exists so that people can build NS-based sites, such as NSDossier and NSEconomy. We want to support such efforts.
Please visit the API documentation page for information. The major change is that very high rates of queries (more than 100/minute) will result in the IP address being denied service for 15 minutes. This is to ensure regular players don't suffer slowdowns because of overzealous scripts.
In general, scripts should not attempt to look up every resident of a region all at once. This can result in dozens, hundreds, or thousands of near-simultaneous requests to the server, which are difficult or impossible to service. If you need information on large numbers of nations, you should trawl them from the API as a speed-limited background job and store the data locally on your server.
Please let me know if you have any questions or concerns!
Background: This is the result of events documented in the "Scripts banned" thread.