Core Data

Here is an impressive quick introduction with a few small videos describing how to create a "Core Data" application from scratch - this is Apple's way of building data-aware apps (using Objective C, Cocoa, Interface Builder, etc).

The interesting pieces are the very slick GUI tools to create a data model, to visually design the GUI, and the way to tie actions and code together. This seems to work with native data formats, SQL,
and XML as storage engines.

A superb intro, though I'm not convinced that this is the way to go, ultimately.