iPhone SDK
As disappointing as the lack of an iPhone Cocoa SDK was at last week's WWDC and the 'controversial' techniques developers are encouraged to use to write applications for the iPhone, there is an application that appears to substantiate Apple's suggestions.
OneTrip is a shopping list web application specifically styled and built for the iPhone. It uses UI metaphors from the iPhone's applications, is styled sympathetically and is designed with features such as drag-scrolling and screen resolution in mind. Data storage happens on the server with cookies managing session identification so there is no user registration or login.
If all iPhone web applications are like this then maybe the current lack of a SDK it isn't such a disaster.