DevX have published an interesting romp through the refactoring of a traditional forms app into a shiny new n-tier architecture utilises MVP.
It compares the difference in coding style between traditional gui programming and MVP, then moves into unit testing, services and dependency injection.
Take a look:
For a less formal and more extensive overview, this series of articles by Jeremy Miller is great:
Build your own CAB (No, not a taxi or a Pocket PC install, but Microsoft Patterns and Practice’s “Composite Application Block”)