The Lotus samples that come with Version 4 don't use the features in Version 4 enough. However, there are several places you can get more samples from:
ComputerWorks has fully functional (limited record input) demo versions of most of
their applications on their web page.
New Information Paradigms has placed a demo application named "Millenia" which they wrote with Lotus UK for demonstrating Notes 4 apps design and Notes 4 & IWP at seminars. It is on their web site here.
Sid Bagali of Parametric has placed a System Inventory example that he put together while learning about Notes V4 features here.
AppJunction Discussion is a Domino-enabled discussion database.