The classic articles about NHibernate, at least for me, are the Server Side .Net ones, here and here, by Justin Gehtland.

There are two example applications for NHibernate: This one by Scott Bellware and this by Paul Wilson. While Cuyahoga is using NHibernate (and my site run on Cuyahoga), I wouldn’t recommend it to a beginner, it is definitely a very advance application.

Benjamin has a lot to say about NHibernate. And Nikola has a very nice introductory post on it here.