It's a Google Custom Search dedicated to helping folks wanting to learn more about NHibernate.
The search index is limited to only highly relevant content, thus making it easier to find good NHibernate content.
This was a pet project of mine, I've always wanted to be able to search a bucket load of good NHibernate reference materials from one place. NHibernate Deep Grok is a solution to that need.
Go check it out, and feel free to help the community and suggest any great NHibernate resources you know about!