The best way to get help with NHibernate is to ask a question on the NHusers Group. When asking a questing remember to provide enough detail so that those who wish to help you can analyze your request when you first make it without having to ask for further details. The various mapping files, query definitions and sometimes configuration or program details should be provided when they are relevant to the discussion.
Google Groups
Other Sources
This site has a search function that may return a relevant answer, from the many Wiki or Blog entries posted here. A Google search will lead to many other blogs with helpful information.
There are 3 books written about NHibernate. They can be seen here with links to buy them. The first 2 were written with NHibernate version 1.2, but still have relevant information for even the latest version, though the feature list has expanded greatly. The 3rd book was written base on version 2.1 and was just released in May 2010.