Puppet Labs released Facter 1.7 this week, introducing a number of under-the-hood enhancements and a new feature called "external facts" that's been waiting in the wings for about a year now.
Facter is a cross-platform library for gathering information about nodes managed by Puppet, including domain names, IP addresses, operating systems, Linux distributions, and more. External facts
provide a simple way for a puppet agent to provide custom facts without having to write Ruby. Eric Sorenson, Puppet's open source product owner, told me, "they're probably the easiest way for people to get an entry into Puppet for extending Puppet or customizing Puppet for their own site."