Common patterns / practices for domain objects and object-relational impedance mismatch?

We're currently developing domain layer for our company's intranet. Basically, we follow a simple and well defined N-Layer pattern from series of articles by Imar Spaanjaars.
We are porting of an existing classic ASP application to ASP.NET 3.5 / C# / SQL Server 2008 environment. Because of that, both business logic and a database are pretty much defined. What we need, however, is some additional guidance on overcoming object-relational impedance mismatch, common design patterns / practices for domain objects which correspond to database objects (tables) with one-to-many, many-to-many, and look-up types of relationships.
Which books/articles would you recommend to read?