Some books on my reading list:
Refactoring to Patterns (0321213351) by Joshua Kerievsky. I've read some pre-publication excerpts from this book. It's a good addition to Martin Fowler's Refactoring book.
Object Oriented Reengineering Patterns (1558606394) by Serge Deymeyer, Stephane Ducasse, Oscar Nierstrasz. Recommended by Michael Feathers:
Sometimes external design reviews devolve into audits.. that whole checklist thing. It happens because it is easier than really going in and groking the design. Successful external reviews target the macro and micro design levels. In a trusting atmosphere you can ask where the code the team is most proud of is, and where the areas of uncertainty are.
One good book that helps for external reviews... (on ExtremeProgramming@yahoogroups mailing list)