I was going to use the NHibernate facility provided by Castle Windsor until I found out it didn't support using class mapping attributes.  I ended up rolling my own implementation but added a couple new features to my implementation:

• Automatic context aware session container (web context or thread local).
• Ability to use NHibernate mapping attributes instead of hbm.xml files.
  
• Can use the built-in .NET 2.0 connectionStrings element to specify an NHibernate connection string.

I think the first two items are pretty obvious, but the last feature I added because most standard .NET applications make use of these elements - for better or worse.  I think its a good idea to be consistent if possible.  Additionally this would allow any standard .NET administration tool to examine and edit the connection string for the application.

I also wanted the ability to use a custom configuration section so that I could add additional elements and attributes as needed.  The configuration section handler produces a SessionFactoryConfiguration instance, which itself it a subclass of NHibernate.Cfg.Configuration.  The configuration section looks like this:

  <sessionManager>
    <settings>
      <setting name="hibernate.dialect">NHibernate.Dialect.MsSql2000Dialect</setting>
      <setting name="hibernate.connection.driver_class">NHibernate.Driver.SqlClientDriver</setting>
      <setting name="dotnet.connection_string">Laptop</setting>
      <setting name="hibernate.connection.provider">
         NHibernate.Connection.DriverConnectionProvider
      </setting>
    </settings>
    <resources>
      <resource assembly="Sneal.Northwind.Core" useAttributes="true"/>
    </resources>
  </sessionManager>

Notice the setting dotnet.connection_string.  This is the custom hook I added to my custom configuration handler that resolves Laptop to the .NET connection string named Laptop:

  <connectionStrings>
    <add name="Laptop" connectionString="Database=Northwind; Data Source=.\sqldev2000;" />
  </connectionStrings>

Then I just wire up my SessionManager instance to my Repository instance using an IoC container; currently Windsor.  I have an HttpModule which handles my Unit of Work currently, but unfortunately its tied to Windsor and my current application, so now I'm off to decouple it for reuse.