From Nagios Support Wiki
Official information on Nagios XI can be found here.
Nagios XI is an enterprise-class monitoring solution that provides organizations with eXtended Insight into their IT infrastructure before problems affect critical business processes. Find out more about XI's capabilities by visiting the product information link:
Video tutorials that guide you through various aspects of XI usage and concepts.
Individual documents that explain various aspects of administering and using Nagios XI.
Answers to Frequently Asked Questions about Nagios XI.
Other Support Resources
Support for Nagios XI is provided via our online support forum at the link below.
Phone and email support contracts for XI are expected to be available in Q1 of 2010.