After a first small update some weeks ago, the NHibernate team released a second update for NHibernate 2.1 last weekend.
NHibernate 2.1.2 can be downloaded here. The list of changes is rather small:
* [NH-2011] - Many-to-many inside a component will not be saved when using SaveOrUpdateCopy or Merge
* [NH-2022] - Allow overriding in Query By Example
* [NH-2007] - SesssionIdLoggingContext patch for big resultsets
* [NH-2019] - Clarification about the use of <import> for polymorphic queries