Speaking of O/R Mappers, if you are into the ActiveRecord Design Pattern and want to use an O/R Mapper that uses the ActiveRecord Pattern, don't forget about Castle ActiveRecord:
”The Castle ActiveRecord project is an implementation of the ActiveRecord pattern for .NET. The ActiveRecord pattern consists on instance properties representing a record in the database, instance methods acting on that specific record and static methods acting on all records. Castle ActiveRecord is built on top of NHibernate, but its attribute-based mapping free the developer of writing XML for database-to-object mapping, which is needed when using NHibernate directly.”
I have talked about ActiveRecord and Castle ActiveRecord quite a bit in the past:
If you are interested in Castle ActiveRecord, The NHibernate FAQ has a new tutorial here on getting started with Castle ActiveRecord.